Transform a string such that it has abcd..z as a subsequence

Transforming a string aka string transformation is an operation in C++ by which the result stores in an output array after the execution of the whole process. In C++ there is a function called "transform()", present in the directory of the C++ environment by which we can transform a string into a new one.

There are two forms of this transform function −

• Unary operation

• Operation applies on the every element of the input array.

• After the operation being done the result will store in an output array.

• Binary operation

• Operation applies on each element of a particular array.

• The first input element and the second respective input element takes a part in the operation.

• The output data will store in an output array.

A subsequence string is a completely new string, generated from the input string by performing various operations (like: deletion) on it. For a subsequence string the operations take place without tampering the remaining characters.

For a string transformation, the input contains the operated string with a length of n+1. Original character is belong to the series of a to z. The printed string's length is considered as n here, which is an output string here.

In this article, we will learn how to transform a string such that it has abcd….z as a subsequence by using a C++ environment.

Algorithm of a subsequent string by recursion

By using recursion approach, here is the possible algorithm for a subsequent string. Here’s is the particular string and T is the consumed time to make the operation done.

• Step 1 − Count Occurrences.

• Step 2 − If, i= length(s) and j= length(T).

• Step 3− Then Return 1.

• Step 4 − End.

• Step 5 − If, i= length(S).

• Step 6 − Then Return 0.

• Step 7 − End.

• Step 8 − Count <-- 0.

• Step 9 − If, j<length (T) AND Si = Tj.

• Step 10 − Count<-- count + countOccurences(i+1,j+1).

• Step 11 − End.

• Step 12 − Count<-- count + countOccurences(i+1,j).

• Step 13 − Return count.

• Step 14 − End.

Syntax of a subsequent array

Here, we have two given sequences. X and Y.
Initialize a table with a dimension of X.length * Y.length
X.label1 = X
Y.label2 = Y
CS1[0][] = 0
CS2[][0] = 0
Start from CS[1][1]
Compare X[i] and Y[j]
   If
      X[i] = Y[j]
      CS[i][j] = 1 + CS[i-1, j-1]
      Point an arrow to CS[i][j]
   Else
      CS[i][j] = max(CS[i-1][j], CS[i][j-1])
      Point an arrow to max(CS[i-1][j], CS[i][j-1])

Here we have created the basic working syntax of a subsequent array. When two sequences are there, we have to follow these steps to get the output.

Approaches to follow

• Approach 1 − Transform a string by using C++

• Approach 2 − Unary operation on a string by using C++

• Approach 3 − Binary operation on a string by using C++

• Approach 4 − Print all possible subsequent string by using C++

• Approach 5 − Transform a string such that it has abcd….z as a subsequence using C++

Transform a string by using C++

In this C++ code, we have created a new string and remove all the vowels from the input string. In output # has been added at the place of those vowels.

Example 1

#include <bits/stdc++.h>
using namespace std;
string change_case(string r) {
   int l = r.length();
   for(int i = 0 ; i < l ; i++) {
      if(r[i] >= 'a' && r[i] <= 'z')
      r[i] = r[i] - 32;
      else if(r[i] >= 'A' && r[i] <= 'Z')
      r[i] = r[i] + 32;
   }
   return r;
}
string delete_vowels(string a) {
   string temp = "";
   int l = a.length();
   for(int i = 0 ; i < l ; i++) {
      if(a[i] != 'a' && a[i] != 'e' &&
      a[i] != 'i' && a[i] != 'o' &&
      a[i] != 'u' && a[i] != 'A' &&
      a[i] != 'E' && a[i] != 'O' &&
      a[i] != 'U'&& a[i] != 'I')
      temp += a[i];
   }
   return temp;
}
string insert_hash(string a) {
   string temp = "";
   int l = a.length();
   for(int i = 0 ; i < l ; i++) {
      if((a[i] >= 'a' && a[i] <= 'z') ||
      (a[i] >= 'A' && a[i] <= 'Z'))
      temp = temp + '#' + a[i];
      else
      temp = temp + a[i];
   }
   return temp;
}
void transformSting(string a) {
   string b = delete_vowels(a);
   string c = change_case(b);
   string d = insert_hash(c);
   if(d=="")
   cout<<"-1"<<endl;
   else
   cout << d<<endl;
}
int main() {
   string a = "RudraDevDas!!";
   string b = "aeiou";
   transformSting(a);
   transformSting(b);
   return 0;
}

Output

#r#D#R#d#V#d#S!!
-1

Unary operation on a string by using C++

In this particular code we have demonstrated how the unary operation works on an input array. The function takes a pointer at starting and ending for a single input. And after operation to the starting position of an output array.

Example 2

#include <iostream>
#include <algorithm>
using namespace std;
int op_increment (int x) {
   x = x + 1;
   return x;
}
int main () {
   int n = 5;
   int input_array[] = {7, 16, 10, 97, 2001};
   int output_array[n];
   std::cout << "Input array present here:";
   for(int i=0; i<5; i++){
      cout << ' ' << input_array[i];
   }
   cout << '\n';
   transform (input_array, input_array+5, output_array, op_increment);
   std::cout << "The output array now contains with:";
   for(int i=0; i<5; i++){
      cout << ' ' << output_array[i];
   }
   cout << '\n';
   return 0;
}

Output

Input array present here: 7 16 10 97 2001
The output array now contains with: 8 17 11 98 2002

Binary operation on a string by using C++

In this particular code we have demonstrated how the binary operation works on an input array. The function transform(), attached a pointer at the starting point and the first input array at the ending point. Remember that, the binary operation always works on two input data set.

Example 3

#include <iostream>
#include <algorithm>
#include <vector>
using namespace std;
int op_add (int i, int j) {
   return i+j;
}
int main () {
   int n = 5;
   int arr1[] = {7, 16, 10, 2001, 1997};
   int arr2[] = {1, 2, 3, 4, 5};
   int output[n];
   std::cout << "Input data in array1:";
   for(int i=0; i<n; i++){
      cout << ' ' << arr1[i];
   }
   cout << '\n';
   std::cout << "Input data in array2:";
   for(int i=0; i<n; i++){
      cout << ' ' << arr2[i];
   }
   cout << '\n';
   std::transform (arr1, arr1+n, arr2, output, op_add);
   std::cout << "Output array is here now:";
   for(int i=0; i<5; i++){
      cout << ' ' << output[i];
   }
   cout << '\n';
   return 0;
}

Output

Input data in array1: 7 16 10 2001 1997
Input data in array2: 1 2 3 4 5
Output array is here now: 8 18 13 2005 2002

Print all subdequent string by using C++

The pick and don’t pick concept are applied to find out all the subsequence of a particular array. Here in the process may be some character can be deleted without changing the order of the elements. Here, this process of the time complexity is O(2^n) and space complexity is O(n).

Example 4

#include <bits/stdc++.h>
using namespace std;
void printSubsequence(string input, string output) {
   if (input.empty()) {
      cout << output << endl;
      return;
   }
   printSubsequence(input.substr(1), output + input[0]);
   printSubsequence(input.substr(1), output);
}
int main() {
   string output = "";
   string input = "rudraabonikoaa";
   printSubsequence(input, output);
   return 0;
}

Output

rudraabonikoaa
rudraabonikoa
rudraabonikoa
rudraaboniko
rudraabonikaa
rudraabonika
rudraabonika
rudraabonik
rudraabonioaa
rudraabonioa
rudraabonioa
rudraabonio
rudraaboniaa
rudraabonia
rudraabonia

Transform a string such that it has abcd…z as a subsequence

Here is the particular process to transform a string such that it has abcd...z as a subsequence.

• Initialize the character.

• If the length is less than 26, return false.

• Iterate the loop to 0 to s.size () -1.

• If character reaches to z, break the loop.

• If the present character is less than s or equal to the character.

• Replace the current character increment by 1.

• If character less than or equal to z, then return false.

• Else, return true.

Here for this process the time complexity is O(n) and the auxiliary space is O(1). Here, n is the length of a particular string.

Example 5

#include <bits/stdc++.h>
using namespace std;
bool transformString(string& s) {
   char ch = 'a';
   if (s.size() < 26)
   return false;
   for (int i = 0; i < s.size(); i++) {
      if (int(ch) > int('z'))
      break;
      if (s[i] <= ch) {
         s[i] = ch;
         ch = char(int(ch) + 1);
      }
   }
   if (ch <= 'z')
   return false;
   return true;
}
int main() {
   string str = "aaaaaaaaaaaaaaaaaaaaaaaaaaa";
   if (transformString(str))
   cout << str << endl;
   else
   cout << "Not Possible" << endl;
   return 0;
}

Output

abcdefghijklmnopqrstuvwxyza

Conclusion

Today in this article we have learned about string transformation and its different forms by using C++ environment. By following the particular algorithm and syntax, we have examined and built some different C++ codes and, came to know how to transform a string such that it has abcd...z as a subsequence.