soj 2652: Oulipo

@(K ACMer)

题意:
寻找第一个字符串在第二个字符串中出现的次数.
分析:
裸跑kmp,模式串后面加一个奇怪字符.

#include <cstdio>
#include <iostream>
#include <cstring>
#include <cstdlib>
#include <string>
#include <vector>
#include <set>
#include <map>
#include <queue>
#include <algorithm>
using namespace std;
const int maxn = 1e6 + 123, INF = 0x3fffffff, mod = 1e9 + 7;
char s[maxn], p[maxn / 100];
int nexts[maxn / 100], plen;

void getnexts(char* p)
{
    int k = -1, j = 0;
    nexts[0] = -1;
    while (j < plen - 1) {
        if (k == -1 || p[j] == p[k]) {
            j++, k++;
            if (p[j] != p[k]) nexts[j] = k;
            else nexts[j] = nexts[k];
        } else {
            k = nexts[k];
        }
    }
}

int kmp(char* s, char* p)
{
    int ret = 0;
    int i = 0, j = 0, slen = strlen(s);
    while (i < slen) {
        if (j == -1 || s[i] == p[j]) {
            i++, j++;
            if (j == plen - 1) ret++;
        } else j = nexts[j];
    }
    return ret;
}

int main(void ){
    int T;
    scanf("%d", &T);
    while (T--) {
        scanf("%s%s", p, s);
        plen = strlen(p);
        p[plen] = '&';
        p[++plen] = '\0';
        getnexts(p);
        printf("%d\n", kmp(s, p));
    }
    return 0;
}