HDU 1686 Oulippo

 

http://acm.hdu.edu.cn/showproblem.php?pid=1686

题意：给定一个文本串和给定一个模式串，求文本串中有几个模式串。

思路：直接套用KMP模板。

#include<iostream> 
#include<cstring>
#include<string>
using namespace std;

const int maxn = 1000000 + 5;

int next[10002], n, m;
char text[maxn], pattern[10002];

void get_next()
{
    int i, j;
    i = -1;
    j = 0;
    ::next[0] = -1;
    while (j<m)
    {
        if (i == -1 || pattern[i] == pattern[j])
        {
            ::next[++j] = ++i;
        }
        else
            i = ::next[i];
    }
}

int KMP()
{
    int i, j, count = 0;
    i = j = 0;
    get_next();
    while (i<n)
    {
        if (j == -1 || text[i] == pattern[j])
        {
            i++;
            j++;
            if (j == m)  count++;
        }
        else
            j = ::next[j];
    }
    return count;
}

int main()
{
    //freopen("D:\\txt.txt", "r", stdin);
    int t, ans;
    cin >> t;
    getchar();
    while (t--)
    {
        scanf("%s", pattern);
        scanf("%s", text);
        n = strlen(text);
        m = strlen(pattern);
        ans = KMP();
        cout << ans << endl;
    }
    return 0;
}