URAL 1423 String Tale

#include<stdio.h>#define MAX_LONG 250001int N;char S[MAX_LONG * 2];char T[MAX_LONG];int next[MAX_LONG];int main(){scanf("%d %s %s", &N, S, T);int len = N * 2;int i;for (i = 0; i < N; i++){S[N + i] = S[i];}S[N + i] = '\0';int prefix = -1;int suffix = 0;next[suffix] = -1;while (suffix < N - 1){if (-1 == prefix || T[prefix] == T[suffix]){prefix++;suffix++;if (T[prefix] != T[suffix]){next[suffix] = prefix;} else {next[suffix] = next[prefix];}} else {prefix = next[prefix];}}int SIndex = 0;int TIndex = 0;while (SIndex < len && TIndex < N){if (S[SIndex] == T[TIndex] || -1 == TIndex){SIndex++;TIndex++;} else {TIndex = next[TIndex];}}int shift = len - SIndex;if (N == shift){printf("0\n");} else if (0 == shift){printf("-1\n");} else {printf("%d\n", shift);}return 0;}