KMP模板

#include <iostream>
#include <cstring>
#include <cstdio>
#include <algorithm>
#include<string>
#include<vector>
#define N 1000010
using namespace std;
int next[N];
char p[N];
char s[N];
int n,m;
void getNext(){
    for(int i = 0; i < n; ++i)next[i] = -1;
    int j = 0, k = -1;
    while(j < m - 1){
        if(k == -1 || p[k] == p[j]){
            ++k;
            ++j;
            if(p[k] != p[j])
                next[j] = k;
            else
                next[j] = next[k];
        }
        else{
            k = next[k];
        }
    }
}

int KMP(){
    int i = 0,j = 0;
    while(i < n && j < m){
        if(j == -1 || s[i] == p[j]){
            ++i;
            ++j;
        }
        else{
            j = next[j];
        }
    }
    printf("i: %d ,j : %d \n",i,j);
    if( j == m) return i - j;
    else
        return -1;
}
int main(){
    while(~scanf("%s%s",&s,&p)){
        n = strlen(s);
        m = strlen(p);
        getNext();
        printf("%d\n",KMP());
    }

    return 0;
}