POJ

题意：求模式串t在主串s中的出现次数。

#include<cstdio>
#include<cstring>
#include<cstdlib>
#include<cctype>
#include<cmath>
#include<iostream>
#include<sstream>
#include<iterator>
#include<algorithm>
#include<string>
#include<vector>
#include<set>
#include<map>
#include<stack>
#include<deque>
#include<queue>
#include<list>
#define lowbit(x) (x & (-x))
const double eps = 1e-8;
inline int dcmp(double a, double b){
    if(fabs(a - b) < eps) return 0;
    return a > b ? 1 : -1;
}
typedef long long LL;
typedef unsigned long long ULL;
const int INT_INF = 0x3f3f3f3f;
const int INT_M_INF = 0x7f7f7f7f;
const LL LL_INF = 0x3f3f3f3f3f3f3f3f;
const LL LL_M_INF = 0x7f7f7f7f7f7f7f7f;
const int dr[] = {0, 0, -1, 1, -1, -1, 1, 1};
const int dc[] = {-1, 1, 0, 0, -1, 1, -1, 1};
const int MOD = 1e9 + 7;
const double pi = acos(-1.0);
const int MAXN = 10000 + 10;
const int MAXT = 1000000 + 10;
using namespace std;
char t[MAXN], s[MAXT];
int _next[MAXN];
int slen, tlen;
void getNext(){
    int j = 0, k = -1;
    _next[0] = -1;
    while(j < tlen){
        if(k == -1 || t[j] == t[k]) _next[++j] = ++k;
        else k = _next[k];
    }
}
int kmp_count(){
    if(slen == 1 && tlen == 1){
        return s[0] == t[0] ? 1 : 0;
    }
    getNext();
    int ans = 0, j = 0;
    for(int i = 0; i < slen; ++i){
        while(j > 0 && s[i] != t[j]) j = _next[j];
        if(s[i] == t[j]) ++j;
        if(j == tlen){
            ++ans;
            j = _next[j];
        }
    }
    return ans;
}
int main(){
    int T;
    scanf("%d", &T);
    while(T--){
        memset(_next, 0, sizeof _next);
        scanf("%s%s", t, s);
        tlen = strlen(t);
        slen = strlen(s);
        printf("%d
", kmp_count());
    }
    return 0;
}