C++ Program to Check Whether a Number is Positive or Negative

In modern programming languages we work with signed numbers and unsigned numbers also. For signed numbers the numbers can be positive or negative or zero. To represent negative numbers, the systems store the numbers in 2?s complement method. In this article we shall discuss how to determine a given number is positive, or negative in C++.

Checking using if-else conditions

The basic sign checking can be done by using if else conditions. The syntax for the if-else conditions is like below ?

Syntax

if <condition> {
   perform action when condition is true
}
else {
   perform action when condition is false
}

Algorithm

Determining positive or negative numbers the algorithm will be like below ?

• take a number input n
• if n < 0, then
• return n as negative number
• otherwise
• return n as positive number

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 keyword">using</span> <span class="token keyword">namespace</span> std<span class="token punctuation">;</span>

string <span class="token function">solve</span><span class="token punctuation">(</span> <span class="token keyword">int</span> n <span class="token punctuation">)</span> <span class="token punctuation">{</span>
   <span class="token keyword">if</span><span class="token punctuation">(</span> n <span class="token operator"><</span> <span class="token number">0</span> <span class="token punctuation">)</span> <span class="token punctuation">{</span>
      <span class="token keyword">return</span> <span class="token string">"Negative"</span><span class="token punctuation">;</span>
   <span class="token punctuation">}</span>
   <span class="token keyword">else</span> <span class="token punctuation">{</span>
      <span class="token keyword">return</span> <span class="token string">"Positive"</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>
   cout <span class="token operator"><<</span> <span class="token string">"The 10 is positive or negative? : "</span> <span class="token operator"><<</span> <span class="token function">solve</span><span class="token punctuation">(</span> <span class="token number">10</span> <span class="token punctuation">)</span> <span class="token operator"><<</span> endl<span class="token punctuation">;</span>
   cout <span class="token operator"><<</span> <span class="token string">"The -24 is positive or negative? : "</span> <span class="token operator"><<</span> <span class="token function">solve</span><span class="token punctuation">(</span> <span class="token operator">-</span><span class="token number">24</span> <span class="token punctuation">)</span> <span class="token operator"><<</span> endl<span class="token punctuation">;</span>
   cout <span class="token operator"><<</span> <span class="token string">"The 18 is positive or negative? : "</span> <span class="token operator"><<</span> <span class="token function">solve</span><span class="token punctuation">(</span> <span class="token number">18</span> <span class="token punctuation">)</span> <span class="token operator"><<</span> endl<span class="token punctuation">;</span>
   cout <span class="token operator"><<</span> <span class="token string">"The -80 is positive or negative? : "</span> <span class="token operator"><<</span> <span class="token function">solve</span><span class="token punctuation">(</span> <span class="token operator">-</span><span class="token number">80</span> <span class="token punctuation">)</span> <span class="token operator"><<</span> endl<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

The 10 is positive or negative? : Positive
The -24 is positive or negative? : Negative
The 18 is positive or negative? : Positive
The -80 is positive or negative? : Negative

Checking using ternary operators

We can remove if-else conditions by using ternary operators. The ternary operator uses two symbols ??? and ?:?. The algorithm is similar. The syntax for the ternary operators are like below ?

Syntax

<condition> ? <true case> : <false case>

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 keyword">using</span> <span class="token keyword">namespace</span> std<span class="token punctuation">;</span>

string <span class="token function">solve</span><span class="token punctuation">(</span> <span class="token keyword">int</span> n <span class="token punctuation">)</span> <span class="token punctuation">{</span>
   string res<span class="token punctuation">;</span>
   res <span class="token operator">=</span> <span class="token punctuation">(</span> n <span class="token operator"><</span> <span class="token number">0</span> <span class="token punctuation">)</span> <span class="token operator">?</span> <span class="token string">"Negative"</span> <span class="token operator">:</span> <span class="token string">"Positive"</span><span class="token punctuation">;</span>
   <span class="token keyword">return</span> res<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>
   cout <span class="token operator"><<</span> <span class="token string">"The 56 is positive or negative? : "</span> <span class="token operator"><<</span> <span class="token function">solve</span><span class="token punctuation">(</span> <span class="token number">56</span> <span class="token punctuation">)</span> <span class="token operator"><<</span> endl<span class="token punctuation">;</span>
   cout <span class="token operator"><<</span> <span class="token string">"The -98 is positive or negative? : "</span> <span class="token operator"><<</span> <span class="token function">solve</span><span class="token punctuation">(</span> <span class="token operator">-</span><span class="token number">98</span> <span class="token punctuation">)</span> <span class="token operator"><<</span> endl<span class="token punctuation">;</span>
   cout <span class="token operator"><<</span> <span class="token string">"The 45 is positive or negative? : "</span> <span class="token operator"><<</span> <span class="token function">solve</span><span class="token punctuation">(</span> <span class="token number">45</span> <span class="token punctuation">)</span> <span class="token operator"><<</span> endl<span class="token punctuation">;</span>
   cout <span class="token operator"><<</span> <span class="token string">"The -158 is positive or negative? : "</span> <span class="token operator"><<</span> <span class="token function">solve</span><span class="token punctuation">(</span> <span class="token operator">-</span><span class="token number">158</span> <span class="token punctuation">)</span> <span class="token operator"><<</span> endl<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

The 56 is positive or negative? : Positive
The -98 is positive or negative? : Negative
The 45 is positive or negative? : Positive
The -158 is positive or negative? : Negative

Conclusion

Checking a given integer is positive or negative in C++ takes is a basic condition checking problem, where we check the given number is less than zero or not, if so, then the number is negative, otherwise it is positive. This can be extended into negative, zero and positive checking by using else-if condition. The similar approach can be used by using ternary operators. In this article we have discussed them both with few examples.