Minimum String in C++

Suppose we have two strings s and t of same length, and both are in lowercase letters. Consider we have rearranged s at first into any order, then count the minimum number of changes needed to turn s into t.

So, if the input is like s = "eccynue", t = "science", then the output will be 2 as if we rearrange "eccynue" to "yccence", then replace y with s and second c with i, it will be "science".

To solve this, we will follow these steps −

  • ret := 0

  • Define two arrays cnt1 to hold frequency of s and cnt2 to hold frequency of t

  • for initialize i := 0, when i < 26, update (increase i by 1), do −

    • ret := ret + max(cnt1[i] - cnt2[i], 0)

  • return ret

Let us see the following implementation to get better understanding −


 Live Demo

#include <bits/stdc++.h>
using namespace std;
class Solution {
   int solve(string s, string t) {
      int ret = 0;
      vector <int> cnt1(26);
      vector <int> cnt2(26);
      for(int i = 0; i < s.size(); i++){
         cnt1[s[i] - 'a']++;
      for(int i = 0; i < t.size(); i++){
         cnt2[t[i] - 'a']++;
      for(int i = 0; i < 26; i++){
         ret += max(cnt1[i] - cnt2[i], 0);
      return ret;
int main(){
   Solution ob;
   cout << (ob.solve("eccynue", "science"));


"eccynue", "science"



Updated on: 02-Sep-2020


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