longestSuffixPrefix.cpp

void longestPrefixSuffix(string &p,int *A,int n){
  A[0]=0;
  int i=1,j=0;
  while(i<n){
    if(p[i]==p[j]){   // match found
      A[i]=j+1;
      i++;
      j++;
    }else if(j==0){
      A[i]=0;
      i++;
    }else j=A[j-1];   // search in the next longest prefix
  }
}