C++ program to remove row or column wise duplicates from matrix of characters

We are given a 2D matrix with rows and columns. The matrix consists of elements in char data type. A method is devised to remove the elements which are duplicated in their respective rows or columns.

In this method, we check if any element is repeating in its row or column for each character. If it is not repeated, we leave it as it was before.

We can store the values occurring in each row and column in a map. After which, we can traverse again and take those values which are appearing only once in their row and column. This would require extra space, and we can do a space-time tradeoff by searching for each element in its row and column. We have used a map to store the character and the count.

<span class="pln">vector</span><span class="pun"><</span><span class="pln">vector</span><span class="str"><char></span><span class="pun">></span><span class="pln"> arr </span><span class="pun">=</span><span class="pln"> </span><span class="pun">{</span><span class="pln">
   </span><span class="pun">{</span><span class="str">'A'</span><span class="pun">,</span><span class="pln"> </span><span class="str">'B'</span><span class="pun">,</span><span class="pln"> </span><span class="str">'E'</span><span class="pun">,</span><span class="pln"> </span><span class="str">'G'</span><span class="pun">,</span><span class="pln"> </span><span class="str">'L'</span><span class="pun">},</span><span class="pln">
   </span><span class="pun">{</span><span class="str">'K'</span><span class="pun">,</span><span class="pln"> </span><span class="str">'M'</span><span class="pun">,</span><span class="pln"> </span><span class="str">'P'</span><span class="pun">,</span><span class="pln"> </span><span class="str">'Q'</span><span class="pun">,</span><span class="pln"> </span><span class="str">'S'</span><span class="pun">},</span><span class="pln">
   </span><span class="pun">{</span><span class="str">'V'</span><span class="pun">,</span><span class="pln"> </span><span class="str">'W'</span><span class="pun">,</span><span class="pln"> </span><span class="str">'T'</span><span class="pun">,</span><span class="pln"> </span><span class="str">'B'</span><span class="pun">,</span><span class="pln"> </span><span class="str">'O'</span><span class="pun">},</span><span class="pln">
   </span><span class="pun">{</span><span class="str">'K'</span><span class="pun">,</span><span class="pln"> </span><span class="str">'H'</span><span class="pun">,</span><span class="pln"> </span><span class="str">'O'</span><span class="pun">,</span><span class="pln"> </span><span class="str">'U'</span><span class="pun">,</span><span class="pln"> </span><span class="str">'P'</span><span class="pun">},</span><span class="pln">
   </span><span class="pun">{</span><span class="str">'P'</span><span class="pun">,</span><span class="pln"> </span><span class="str">'I'</span><span class="pun">,</span><span class="pln"> </span><span class="str">'C'</span><span class="pun">,</span><span class="pln"> </span><span class="str">'Y'</span><span class="pun">,</span><span class="pln"> </span><span class="str">'J'</span><span class="pun">},</span><span class="pln">
   </span><span class="pun">{</span><span class="str">'F'</span><span class="pun">,</span><span class="pln"> </span><span class="str">'S'</span><span class="pun">,</span><span class="pln"> </span><span class="str">'K'</span><span class="pun">,</span><span class="pln"> </span><span class="str">'E'</span><span class="pun">,</span><span class="pln"> </span><span class="str">'W'</span><span class="pun">},</span><span class="pln">
   </span><span class="pun">{</span><span class="str">'N'</span><span class="pun">,</span><span class="pln"> </span><span class="str">'L'</span><span class="pun">,</span><span class="pln"> </span><span class="str">'Y'</span><span class="pun">,</span><span class="pln"> </span><span class="str">'G'</span><span class="pun">,</span><span class="pln"> </span><span class="str">'O'</span><span class="pun">},</span><span class="pln">
</span><span class="pun">};</span><span class="pln">
res </span><span class="pun">=</span><span class="pln"> solve</span><span class="pun">(</span><span class="pln">arr</span><span class="pun">);</span>

Example (Using Vector ADT)

Suppose we have a matrix with the following characters ?

<span class="pln">A C E G I
K M O Q S
U W Y B D
K H I N P
R T W X Z
A E I M Q
L O P G A</span>

Here, for the first row of the matrix, we cannot consider ?A? and ?G? because they occur twice in their respective columns, but we can consider ?C?, ?E?, ?I?. Following is a C++ program for the above example ?

<div class="execute"></div><div class="code-mirror  language-cpp" contenteditable="plaintext-only" spellcheck="false" style="outline: none; overflow-wrap: break-word; overflow-y: auto; white-space: pre-wrap;"><span class="token macro property"><span class="token directive-hash">#</span><span class="token directive keyword">include</span> <span class="token string"><iostream></span></span>
<span class="token macro property"><span class="token directive-hash">#</span><span class="token directive keyword">include</span> <span class="token string"><vector></span></span>
<span class="token macro property"><span class="token directive-hash">#</span><span class="token directive keyword">include</span> <span class="token string"><map></span></span>
<span class="token keyword">using</span> <span class="token keyword">namespace</span> std<span class="token punctuation">;</span>
<span class="token keyword">void</span> <span class="token function">solve</span><span class="token punctuation">(</span>vector<span class="token operator"><</span>vector<span class="token operator"><</span><span class="token keyword">char</span><span class="token operator">>></span><span class="token operator">&</span> arr<span class="token punctuation">)</span> <span class="token punctuation">{</span>
   vector<span class="token operator"><</span>map<span class="token operator"><</span><span class="token keyword">char</span><span class="token punctuation">,</span> <span class="token keyword">int</span><span class="token operator">>></span> <span class="token function">rows</span><span class="token punctuation">(</span>arr<span class="token punctuation">.</span><span class="token function">size</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">,</span> <span class="token function">columns</span><span class="token punctuation">(</span>arr<span class="token punctuation">[</span><span class="token number">0</span><span class="token punctuation">]</span><span class="token punctuation">.</span><span class="token function">size</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
   <span class="token keyword">for</span><span class="token punctuation">(</span><span class="token keyword">int</span> i<span class="token operator">=</span><span class="token number">0</span><span class="token punctuation">;</span>i<span class="token operator"><</span>arr<span class="token punctuation">.</span><span class="token function">size</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>i<span class="token operator">++</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
      <span class="token keyword">for</span><span class="token punctuation">(</span><span class="token keyword">int</span> j<span class="token operator">=</span><span class="token number">0</span><span class="token punctuation">;</span>j<span class="token operator"><</span>arr<span class="token punctuation">[</span>i<span class="token punctuation">]</span><span class="token punctuation">.</span><span class="token function">size</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>j<span class="token operator">++</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
         rows<span class="token punctuation">[</span>i<span class="token punctuation">]</span><span class="token punctuation">[</span>arr<span class="token punctuation">[</span>i<span class="token punctuation">]</span><span class="token punctuation">[</span>j<span class="token punctuation">]</span><span class="token punctuation">]</span><span class="token operator">++</span><span class="token punctuation">;</span>
         columns<span class="token punctuation">[</span>j<span class="token punctuation">]</span><span class="token punctuation">[</span>arr<span class="token punctuation">[</span>i<span class="token punctuation">]</span><span class="token punctuation">[</span>j<span class="token punctuation">]</span><span class="token punctuation">]</span><span class="token operator">++</span><span class="token punctuation">;</span>
      <span class="token punctuation">}</span>
   <span class="token punctuation">}</span>
   <span class="token keyword">for</span><span class="token punctuation">(</span><span class="token keyword">int</span> i<span class="token operator">=</span><span class="token number">0</span><span class="token punctuation">;</span>i<span class="token operator"><</span>arr<span class="token punctuation">.</span><span class="token function">size</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>i<span class="token operator">++</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
      <span class="token keyword">for</span><span class="token punctuation">(</span><span class="token keyword">int</span> j<span class="token operator">=</span><span class="token number">0</span><span class="token punctuation">;</span>j<span class="token operator"><</span>arr<span class="token punctuation">[</span>i<span class="token punctuation">]</span><span class="token punctuation">.</span><span class="token function">size</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>j<span class="token operator">++</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
         <span class="token keyword">if</span><span class="token punctuation">(</span>rows<span class="token punctuation">[</span>i<span class="token punctuation">]</span><span class="token punctuation">[</span>arr<span class="token punctuation">[</span>i<span class="token punctuation">]</span><span class="token punctuation">[</span>j<span class="token punctuation">]</span><span class="token punctuation">]</span> <span class="token operator">==</span> <span class="token number">1</span> <span class="token operator">&&</span> columns<span class="token punctuation">[</span>j<span class="token punctuation">]</span><span class="token punctuation">[</span>arr<span class="token punctuation">[</span>i<span class="token punctuation">]</span><span class="token punctuation">[</span>j<span class="token punctuation">]</span><span class="token punctuation">]</span> <span class="token operator">==</span> <span class="token number">1</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
            cout <span class="token operator"><<</span> arr<span class="token punctuation">[</span>i<span class="token punctuation">]</span><span class="token punctuation">[</span>j<span class="token punctuation">]</span><span class="token punctuation">;</span>
         <span class="token punctuation">}</span>
      <span class="token punctuation">}</span>
   <span class="token punctuation">}</span>
<span class="token punctuation">}</span>
<span class="token keyword">int</span> <span class="token function">main</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
   vector<span class="token operator"><</span>vector<span class="token operator"><</span><span class="token keyword">char</span><span class="token operator">>></span> arr <span class="token operator">=</span> <span class="token punctuation">{</span>
      <span class="token punctuation">{</span><span class="token string">'A'</span><span class="token punctuation">,</span> <span class="token string">'C'</span><span class="token punctuation">,</span> <span class="token string">'E'</span><span class="token punctuation">,</span> <span class="token string">'G'</span><span class="token punctuation">,</span> <span class="token string">'I'</span><span class="token punctuation">}</span><span class="token punctuation">,</span>
      <span class="token punctuation">{</span><span class="token string">'K'</span><span class="token punctuation">,</span> <span class="token string">'M'</span><span class="token punctuation">,</span> <span class="token string">'O'</span><span class="token punctuation">,</span> <span class="token string">'Q'</span><span class="token punctuation">,</span> <span class="token string">'S'</span><span class="token punctuation">}</span><span class="token punctuation">,</span>
      <span class="token punctuation">{</span><span class="token string">'U'</span><span class="token punctuation">,</span> <span class="token string">'W'</span><span class="token punctuation">,</span> <span class="token string">'Y'</span><span class="token punctuation">,</span> <span class="token string">'B'</span><span class="token punctuation">,</span> <span class="token string">'D'</span><span class="token punctuation">}</span><span class="token punctuation">,</span>
      <span class="token punctuation">{</span><span class="token string">'K'</span><span class="token punctuation">,</span> <span class="token string">'H'</span><span class="token punctuation">,</span> <span class="token string">'I'</span><span class="token punctuation">,</span> <span class="token string">'N'</span><span class="token punctuation">,</span> <span class="token string">'P'</span><span class="token punctuation">}</span><span class="token punctuation">,</span>
      <span class="token punctuation">{</span><span class="token string">'R'</span><span class="token punctuation">,</span> <span class="token string">'T'</span><span class="token punctuation">,</span> <span class="token string">'W'</span><span class="token punctuation">,</span> <span class="token string">'X'</span><span class="token punctuation">,</span> <span class="token string">'Z'</span><span class="token punctuation">}</span><span class="token punctuation">,</span>
      <span class="token punctuation">{</span><span class="token string">'A'</span><span class="token punctuation">,</span> <span class="token string">'E'</span><span class="token punctuation">,</span> <span class="token string">'I'</span><span class="token punctuation">,</span> <span class="token string">'M'</span><span class="token punctuation">,</span> <span class="token string">'Q'</span><span class="token punctuation">}</span><span class="token punctuation">,</span>
      <span class="token punctuation">{</span><span class="token string">'L'</span><span class="token punctuation">,</span> <span class="token string">'O'</span><span class="token punctuation">,</span> <span class="token string">'P'</span><span class="token punctuation">,</span> <span class="token string">'G'</span><span class="token punctuation">,</span> <span class="token string">'A'</span><span class="token punctuation">}</span><span class="token punctuation">,</span>
   <span class="token punctuation">}</span><span class="token punctuation">;</span>
   <span class="token function">solve</span><span class="token punctuation">(</span>arr<span class="token punctuation">)</span><span class="token punctuation">;</span>
   <span class="token keyword">return</span> <span class="token number">0</span><span class="token punctuation">;</span>
<span class="token punctuation">}</span>
</div><div class="output-wrapper"><div class="console-close"></div><div class="code-output"></div></div>

Output

CEIMOQSUWYBDHNPRTWXZEMQLOPA

Example (Without Using Vector ADT)

<div class="execute"></div><div class="code-mirror  language-cpp" contenteditable="plaintext-only" spellcheck="false" style="outline: none; overflow-wrap: break-word; overflow-y: auto; white-space: pre-wrap;"><span class="token macro property"><span class="token directive-hash">#</span><span class="token directive keyword">include</span> <span class="token string"><bits/stdc++.h></span></span>
<span class="token keyword">using</span> <span class="token keyword">namespace</span> std<span class="token punctuation">;</span>
<span class="token keyword">int</span> <span class="token function">main</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
   <span class="token keyword">int</span> row <span class="token operator">=</span> <span class="token number">2</span><span class="token punctuation">,</span> column <span class="token operator">=</span> <span class="token number">8</span><span class="token punctuation">;</span>
   <span class="token keyword">const</span> <span class="token keyword">char</span><span class="token operator">*</span> input_array<span class="token punctuation">[</span><span class="token punctuation">]</span> <span class="token operator">=</span> <span class="token punctuation">{</span> <span class="token string">"ABCDPQST"</span><span class="token punctuation">,</span> <span class="token string">"ECFDOMUT"</span> <span class="token punctuation">}</span><span class="token punctuation">;</span>

   <span class="token keyword">bool</span> boolean_array<span class="token punctuation">[</span>row<span class="token punctuation">]</span><span class="token punctuation">[</span>column<span class="token punctuation">]</span><span class="token punctuation">;</span>
   <span class="token function">memset</span><span class="token punctuation">(</span>boolean_array<span class="token punctuation">,</span> <span class="token number">0</span><span class="token punctuation">,</span> <span class="token keyword">sizeof</span><span class="token punctuation">(</span>boolean_array<span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">;</span>

   <span class="token keyword">for</span> <span class="token punctuation">(</span><span class="token keyword">int</span> i <span class="token operator">=</span> <span class="token number">0</span><span class="token punctuation">;</span> i <span class="token operator"><</span> row<span class="token punctuation">;</span> i<span class="token operator">++</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
      <span class="token keyword">for</span> <span class="token punctuation">(</span><span class="token keyword">int</span> j <span class="token operator">=</span> <span class="token number">0</span><span class="token punctuation">;</span> j <span class="token operator"><</span> column<span class="token punctuation">;</span> j<span class="token operator">++</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
          
         <span class="token keyword">for</span> <span class="token punctuation">(</span><span class="token keyword">int</span> k <span class="token operator">=</span> <span class="token number">0</span><span class="token punctuation">;</span> k <span class="token operator"><</span> column<span class="token punctuation">;</span> k<span class="token operator">++</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
            <span class="token keyword">if</span> <span class="token punctuation">(</span>input_array<span class="token punctuation">[</span>i<span class="token punctuation">]</span><span class="token punctuation">[</span>j<span class="token punctuation">]</span> <span class="token operator">==</span> input_array<span class="token punctuation">[</span>i<span class="token punctuation">]</span><span class="token punctuation">[</span>k<span class="token punctuation">]</span> <span class="token operator">&&</span> j <span class="token operator">!=</span> k<span class="token punctuation">)</span> <span class="token punctuation">{</span>
                boolean_array<span class="token punctuation">[</span>i<span class="token punctuation">]</span><span class="token punctuation">[</span>j<span class="token punctuation">]</span> <span class="token operator">=</span> <span class="token boolean">true</span><span class="token punctuation">;</span>
                boolean_array<span class="token punctuation">[</span>i<span class="token punctuation">]</span><span class="token punctuation">[</span>k<span class="token punctuation">]</span> <span class="token operator">=</span> <span class="token boolean">true</span><span class="token punctuation">;</span>
            <span class="token punctuation">}</span>
         <span class="token punctuation">}</span>
         <span class="token keyword">for</span> <span class="token punctuation">(</span><span class="token keyword">int</span> k <span class="token operator">=</span> <span class="token number">0</span><span class="token punctuation">;</span> k <span class="token operator"><</span> row<span class="token punctuation">;</span> k<span class="token operator">++</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
            <span class="token keyword">if</span> <span class="token punctuation">(</span>input_array<span class="token punctuation">[</span>i<span class="token punctuation">]</span><span class="token punctuation">[</span>j<span class="token punctuation">]</span> <span class="token operator">==</span> input_array<span class="token punctuation">[</span>k<span class="token punctuation">]</span><span class="token punctuation">[</span>j<span class="token punctuation">]</span> <span class="token operator">&&</span> i <span class="token operator">!=</span> k<span class="token punctuation">)</span> <span class="token punctuation">{</span>
                boolean_array<span class="token punctuation">[</span>i<span class="token punctuation">]</span><span class="token punctuation">[</span>j<span class="token punctuation">]</span> <span class="token operator">=</span> <span class="token boolean">true</span><span class="token punctuation">;</span>
                boolean_array<span class="token punctuation">[</span>k<span class="token punctuation">]</span><span class="token punctuation">[</span>j<span class="token punctuation">]</span> <span class="token operator">=</span> <span class="token boolean">true</span><span class="token punctuation">;</span>
            <span class="token punctuation">}</span>
         <span class="token punctuation">}</span>
      <span class="token punctuation">}</span>
   <span class="token punctuation">}</span>
   <span class="token keyword">for</span> <span class="token punctuation">(</span><span class="token keyword">int</span> i <span class="token operator">=</span> <span class="token number">0</span><span class="token punctuation">;</span> i <span class="token operator"><</span> row<span class="token punctuation">;</span> i<span class="token operator">++</span><span class="token punctuation">)</span>
   <span class="token keyword">for</span> <span class="token punctuation">(</span><span class="token keyword">int</span> j <span class="token operator">=</span> <span class="token number">0</span><span class="token punctuation">;</span> j <span class="token operator"><</span> column<span class="token punctuation">;</span> j<span class="token operator">++</span><span class="token punctuation">)</span>
   <span class="token keyword">if</span> <span class="token punctuation">(</span><span class="token operator">!</span>boolean_array<span class="token punctuation">[</span>i<span class="token punctuation">]</span><span class="token punctuation">[</span>j<span class="token punctuation">]</span><span class="token punctuation">)</span>
      <span class="token function">printf</span><span class="token punctuation">(</span><span class="token string">"%c "</span><span class="token punctuation">,</span> input_array<span class="token punctuation">[</span>i<span class="token punctuation">]</span><span class="token punctuation">[</span>j<span class="token punctuation">]</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
   <span class="token keyword">return</span> <span class="token number">0</span><span class="token punctuation">;</span>
<span class="token punctuation">}</span>
</div><div class="output-wrapper"><div class="console-close"></div><div class="code-output"></div></div>

Output

A B C P Q S E C F O M U

Conclusion

We have used O(n^2) complexity. The log(n) complexity of the map can be ignored for only lower case Latin characters as there are 26 characters only. But for a character of more random characters, this might come into play. You can try solving this problem without using hashing and extra space for yourself.