HDU 2087 剪花布条（kmp）

最新推荐文章于 2019-04-16 19:23:42 发布

TaoSama

最新推荐文章于 2019-04-16 19:23:42 发布

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分类专栏：字符串字符串 - KMP | EXKMP | Manacher 文章标签： kmp

本文链接：https://blog.youkuaiyun.com/lwt36/article/details/49497291

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本文介绍了如何使用KMP算法解决字符串匹配问题，特别是针对母串中出现模式串次数的计算，并提供了两种实现方式：一种是利用KMP算法进行高效匹配，另一种则是通过简单的strstr函数实现。

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题意:

$求母串中出现了几次模式串, 不能重叠$

分析:

$kmp匹配到了之后从头开始就好了$

代码:

//
//  Created by TaoSama on 2015-10-27
//  Copyright (c) 2015 TaoSama. All rights reserved.
//
//#pragma comment(linker, "/STACK:1024000000,1024000000")
#include <algorithm>
#include <cctype>
#include <cmath>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <iomanip>
#include <iostream>
#include <map>
#include <queue>
#include <string>
#include <set>
#include <vector>

using namespace std;
#define pr(x) cout << #x << " = " << x << "  "
#define prln(x) cout << #x << " = " << x << endl
const int N = 1e5 + 10, INF = 0x3f3f3f3f, MOD = 1e9 + 7;

int n, m, nxt[1005];
char s[1005], t[1005];

void getNxt() {
    nxt[0] = -1;
    int i = 0, j = -1;
    while(i < m) {
        if(j == -1 || t[i] == t[j]) nxt[++i] = ++j;
        else j = nxt[j];
    }
}

int kmp() {
    int i = 0, j = 0, ret = 0;
    while(i < n) {
        if(j == -1 || s[i] == t[j]) ++i, ++j;
        else j = nxt[j];
        if(j == m) j = 0, ++ret;
    }
    return ret;
}

int main() {
#ifdef LOCAL
    freopen("C:\\Users\\TaoSama\\Desktop\\in.txt", "r", stdin);
//  freopen("C:\\Users\\TaoSama\\Desktop\\out.txt","w",stdout);
#endif
    ios_base::sync_with_stdio(0);

    while(scanf("%s", s) == 1 && *s != '#') {
        scanf("%s", t);
        n = strlen(s), m = strlen(t);
        getNxt();
        printf("%d\n", kmp());
    }
    return 0;
}

$暴力strstr也可以\ 数据小$
代码:

//
//  Created by TaoSama on 2015-10-27
//  Copyright (c) 2015 TaoSama. All rights reserved.
//
//#pragma comment(linker, "/STACK:1024000000,1024000000")
#include <algorithm>
#include <cctype>
#include <cmath>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <iomanip>
#include <iostream>
#include <map>
#include <queue>
#include <string>
#include <set>
#include <vector>

using namespace std;
#define pr(x) cout << #x << " = " << x << "  "
#define prln(x) cout << #x << " = " << x << endl
const int N = 1e5 + 10, INF = 0x3f3f3f3f, MOD = 1e9 + 7;

char s[1005], t[1005];

int main() {
#ifdef LOCAL
    freopen("C:\\Users\\TaoSama\\Desktop\\in.txt", "r", stdin);
//  freopen("C:\\Users\\TaoSama\\Desktop\\out.txt","w",stdout);
#endif
    ios_base::sync_with_stdio(0);

    while(scanf("%s", s) == 1 && *s != '#') {
        scanf("%s", t);
        int ans = 0, m = strlen(t);
        char *p = s;
        while(p = strstr(p, t)) {
            p += m;
            ++ans;
        }
        printf("%d\n", ans);
    }
    return 0;
}