hdu2328Corporate Identity

题目链接：http://acm.hdu.edu.cn/showproblem.php?pid=2328
找一个字典序最小的公共最长子串，枚举子串暴力就能过，这里有个小优化就是选取最短的字符串枚举其子串。

#include <stdio.h>
#include<iostream>
#include<cstring>
#include<cstdlib>
#include<cmath>
using namespace std;
char p[205][205];
char str1[205];
int len[205];
char ast[205];
int nxt[205];
void gnx(char str[],int len){
    memset(nxt,0,sizeof(nxt));
    int i=0,j=-1;
    nxt[0]=-1;
    while(i<len){
        if(j==-1||str[i]==str[j]){
            if(str[++i]==str[++j])nxt[i]=nxt[j];
            else nxt[i]=j;
        }
        else j=nxt[j];
    }
}
int kmp(char s[],int ls,char p[],int lp){
    int i=0,j=0;
    while(i<ls&&j<lp){
        if(j==-1||s[i]==p[j]){++i;++j;}
        else j=nxt[j];
    }
    if(j==lp)return i-lp;
    else return -1;
}
int sstrcmp(char a[],char b[],int len){
    int i=0;
    while(i<len){
        if(a[i]<b[i])return -1;
        else if(a[i]>b[i])return 1;
        else i++;
    }
    return 0;
}
int main(void)
{
    int n;

    while (~scanf("%d", &n) && n)
    {
        int ans = 0;
        int st = 0, mn = 1000;

        for (int i = 1; i <= n; i++)
        {
            scanf("%s", p[i]);
            len[i] = strlen(p[i]);

            if (len[i] < mn)
            {
                mn = len[i];
                st = i;
            }
        }
        for(int i=0;i<mn;i++){
            memcpy(str1,p[st]+i,mn-i);
            str1[mn-i]=0;
            gnx(str1,mn-i);
            for(int j=max(ans,1);j<=mn-i;j++){
                int flag=1;
                for(int k=1;k<=n;k++){
                    if(k==st)continue;
                    if(kmp(p[k],len[k],str1,j)==-1){flag=0;break;}
                }
                if(flag){
                    if(j>ans||((j==ans)&&sstrcmp(ast,str1,j)>0)){ans=j;memcpy(ast,str1,j);ast[j]=0;}
                }
            }
        }
        if(ans==0)puts("IDENTITY LOST");
        else printf("%s\n",ast);
    }

    return 0;
}