C++ Program to Check if strings are rotations of each other or not | Set 2

// C++ program to check if 
// two strings are rotations
// of each other
#include<bits/stdc++.h>
using namespace std;
bool isRotation(string a, 
                string b)
{
  int n = a.length();
  int m = b.length();
  if (n != m)
    return false;

  // create lps[] that 
  // will hold the longest
  // prefix suffix values 
  // for pattern
  int lps[n];

  // length of the previous 
  // longest prefix suffix
  int len = 0;
  int i = 1;
  
  // lps[0] is always 0
  lps[0] = 0; 

  // the loop calculates 
  // lps[i] for i = 1 to n-1
  while (i < n) 
  {
    if (a[i] == b[len]) 
    {
      lps[i] = ++len;
      ++i;
    }
    else 
    {
      if (len == 0) 
      {
        lps[i] = 0;
        ++i;
      }
      else 
      {
        len = lps[len - 1];
      }
    }
  }

  i = 0;

  // Match from that rotating
  // point
  for (int k = lps[n - 1]; 
           k < m; ++k) 
  {
    if (b[k] != a[i++])
      return false;
  }
  return true;
}

// Driver code
int main()
{
  string s1 = "ABACD";
  string s2 = "CDABA";
  cout << (isRotation(s1, s2) ? 
           "1" : "0");
}

// This code is contributed by Chitranayal