hdu 2594 Simpsons’ Hidden Talents 【KMP】

题目链接：http://acm.acmcoder.com/showproblem.php?pid=2594

题意：求最长的串 同一时候是s1的前缀又是s2的后缀。输出子串和长度。

思路：kmp

代码：

#include <vector>
#include <string>
#include <algorithm>
#include <iostream>
#include <stdio.h>
#include <string.h>

using namespace std;

char s1[500010],s2[500010];
char ANS[500010];

void get_next(char x[], int m, int Next[])
{
    int i, j;
    j = Next[0] = -1;
    i = 0;
    while (i < m)
    {
        while (-1 != j && x[i] != x[j]) j = Next[j];
        Next[++i] = ++j;
    }
}

int Next[1001000];
int KMP(char x[], int m, char y[], int n)//x模式串 y主串
{
    int i, j;
    i = j = 0;
    get_next(x, m, Next);
    if (n > m) i = n - m;

    while (i < n)
    {
         if (j == -1 || y[i] == x[j])
        {
            i++;
            j++;
        }
        else j = Next[j];
    }
    return j;
}

int main()
{
    while (cin>>s1>>s2)
    {
        int len1 = strlen(s1);
        int len2 = strlen(s2);
        int ans =  KMP(s1, len1, s2, len2);
        if (ans !=0 )
        {
            for(int i=0;i<ans;i++) cout<<s1[i];cout<<" ";
        }
        cout<<ans<<endl;
    }
    return 0;
}