Minimum Move to End Operations to Make All Strings Equal in C++

Problem statement

Given n strings that are permutations of each other. We need to make all strings same with an operation that moves first character of any string to the end of it.

Example

If arr[] = {“abcd”, “cdab”} then 2 moves are required.

• Let us take first string “abcd”. Move character ‘a’ to the end of the string. After this operation string becomes “bcda”
• Now move character ‘b’ to the end of the string. After this operation string becomes “cdab”. Which in turn makes both strings equal

Algorithm

• Take first string. Let us call it as ‘str1’.

• Create a temp string by concating str1 to str1 as follows −

  temp = str1 + str1

• Count rotations required to make all other strings same as current target
• Repeat above steps for all string and return the minimum of all counts.

Example

#include <iostream>
#include <string>
#include <algorithm>
#include <climits>
#define SIZE(arr) (sizeof(arr) / sizeof(arr[0]))
using namespace std;
int minMoves(string str[], int n) {
   int minCnt = INT_MAX;
   for (int i = 0; i < n; ++i) {
      int cnt = 0;
      for (int j = 0; j < n; ++j) {
         string temp = str[j] + str[j];
         int index = temp.find(str[i]);
         if (index != string::npos) {
            cnt += index;
         }
      }
      minCnt = min(cnt, minCnt);
   }
   return minCnt;
}
int main() {
   string str[] = {"abcd", "cdab", "bacd", "cdba"};
   cout << "Minimum moves: " << minMoves(str, SIZE(str)) << endl;
   return 0;
}

Output

When you compile and execute above program. It generates following output −

Minimum moves: 2