acwing 831 KMP字元串

題面

題解

KMP 模闆題 ，next[i]=j 以 i 為終點的字尾和從1開始的非平凡字首最大重合是 j ，下标從1開始

代碼

#include<iostream>
#include<cstdio>
#include<string>
#include<cstring>
#include<algorithm>

using namespace std;
const int N = 1e6 + 10;

int n, m;
char s[N], p[N];
int ne[N];

int main() {

    cin >> n >> p + 1 >> m >> s + 1;

    //求ne數組,下标從1開始
    for (int i = 2, j = 0; i <= n; i++) {
        while (j && p[i] != p[j + 1]) j = ne[j];
        if (p[i] == p[j + 1]) j++;
        ne[i] = j;
    }

    for (int i = 1, j = 0; i <= m; i++) {
        while (j && s[i] != p[j + 1]) j = ne[j];
        if (s[i] == p[j + 1]) j++;
        if (j == n) {
            cout << i-n << " ";
            j = ne[j];
        }
    }

    return 0;
}