POJ3461（KMP模板題）

不多說先粘代碼

#include <iostream>
#include <cstdio>
#include <cstring>
using namespace std;
const int maxn = 1000000+5;
char text[maxn];
char pat[10000 + 5];
int nex[10005];
int cnt;
void Build()
{
    int len = strlen(pat);
    int k = 0;
    nex[0] = -1;
    nex[1] = 0;
    for (int i = 2; i <= len; i++) {
        while (k >= 0 && pat[i-1] != pat[k]) k = nex[k];
        nex[i] = ++k;
    }
}

void KMP()
{
    int len_pat = strlen(pat), len_text = strlen(text);
    if (len_pat < 1 || len_text < 1 || len_pat > len_text)
        return;
    int i = 0, j = 0;
    while (i < len_text) {
        if (j == -1 || pat[j] == text[i]) {
            i++;j++;
        }
        else
            j = nex[j];
        if (j == len_pat) {
            cnt++;
            j = nex[j];
        }
    }
}

int main()
{
    //freopen("in", "r", stdin);
    int t;
    cin >> t;
    while (t--) {
        scanf("%s", pat);
        scanf("%s", text);
        //printf("%s\n", pat);
        //printf("%s\n", text);
        cnt = 0;
        memset(nex, 0, sizeof(nex));
        Build();
        KMP();
        cout << cnt << endl;
    }
    return 0;
}