HDU 2594 KMP

Posted 2020-09-11 Ritchie丶

题目链接

题意：给定两个字符串s1,s2,求最长的s1前缀s使得s为s2的最长后缀,输出该字符串和其长度。

题解：调换s1和s2的顺序，用KMP求解即可。

 

#include <bits/stdc++.h>
using namespace std;
const int N=50005;
char s1[N],s2[N];
int len1,len2;
int next_val[N];
void getnext_val()
{
    int i=0,j=-1; next_val[i]=-1;
    while(i<len2){
        if(j==-1||s2[i]==s2[j]){
            i++;j++;
            if(s2[i]!=s2[j])next_val[i]=j;
            else next_val[i]=next_val[j];
        }
        else j=next_val[j];
    }
}
int kmp()
{
    int i=0,j=0;
    while(i<len1){
        if(j==-1||s1[i]==s2[j]){
            i++;
            j++;
        }
        else j=next_val[j];
    }
    return j;
}
int main()
{
    while(scanf("%s%s",s2,s1)!=EOF){
        len1=strlen(s1);
        len2=strlen(s2);
        getnext_val();
        int k=kmp();
        if(k==0) printf("0\\n");
        else{
            for(int i=0;i<k;i++) printf("%c",s2[i]);
            printf(" %d\\n",k);
        }
    }
    return 0;
}
/*
clinton
homer
riemann
marjorie
*/

 

附上几个传送门：

http://www.cnblogs.com/kuangbin/archive/2012/08/14/2638803.html

http://blog.csdn.net/xingyeyongheng/article/details/9285989

http://www.cnblogs.com/Su-Blog/archive/2012/09/13/2684049.html