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  • 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;
    }
    

      

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  • 原文地址:https://www.cnblogs.com/tyty-Somnuspoppy/p/7122087.html
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