Isomorphic Strings in C++

Suppose we have two strings s and t; we have to check whether they are isomorphic or not. Two strings are said to be isomorphic if the characters in s can be replaced to get t.

All occurrences of a character must be replaced with another character while preserving the order of characters. No two characters may map to the same character but a character may map to itself.

So, if the input is like s = "egg", t = "add”, then the output will be true, as e can map to a, and g can map to d.

To solve this, we will follow these steps −

• Define an array arr of size 256 and fill with -1

• Define an array visited of size 256 and fill with 0

• Define an array visited1 of size 256 and fill with 0

• for initialize i := 0, when i < length of s, update (increase i by 1), do −

  • if visited[s[i]] is same as 1 or visited1[t[i]] is same as 1, then −

    • if arr[s[i]] is not equal to t[i] - ASCII of 'a', then −

      • return false

  • Otherwise

    • visited[s[i]] := 1

    • visited1[t[i]] := 1

    • arr[s[i]] := t[i] - ASCII of 'a'

• return true

Example 

Let us see the following implementation to get better understanding −

 Live Demo

#include <bits/stdc++.h>
using namespace std;
class Solution {
public:
   bool isIsomorphic(string s, string t) {
      vector<int> arr(256, -1);
      vector<bool> visited(256, 0);
      vector<bool> visited1(256, 0);
      for (int i = 0; i < s.length(); i++) {
         if (visited[s[i]] == 1 || visited1[t[i]] == 1) {
            if (arr[s[i]] != t[i] - 'a') {
               return false;
            }
         }
         else {
            visited[s[i]] = 1;
            visited1[t[i]] = 1;
            arr[s[i]] = t[i] - 'a';
         }
      }
      return true;
   }
};
main(){
   Solution ob;
   cout << (ob.isIsomorphic("sky","fry"));
}

Input

"sky","fry"

Output

1