HDU 2328 Corporate Identity

寻找多个字符串中的最长公共子串并输出。

先枚举第一个或者是最短的字符串的所有子串，然后一个一个用KMP匹配就好。

枚举的姿势够好应该不会超时

#include <cstdio>
#include <sstream>
#include <fstream>
#include <cstring>
#include <iostream>
#include <algorithm>
#include <map>
#include <cctype>
#include <ctime>
#include <set>
#include <climits>
#include <vector>
#include <queue>
#include <stack>
#include <cstdlib>
#include <cmath>
#include <string>
#include <list>

#define INPUT_FILE "in.txt"
#define OUTPUT_FILE "out.txt"

using namespace std;

typedef long long LL;
const int INF = INT_MAX / 2;

void setfile() {
    freopen(INPUT_FILE,"r",stdin);
    freopen(OUTPUT_FILE,"w",stdout);
}

const int maxn = 4000 + 5;
const int maxlen = 205;

char dict[maxn][maxlen];
char ans[maxlen];
int f[maxlen];

void getfail(char *str,int len) {
    f[0] = f[1] = 0;
    for(int i = 2;i <= len;i++) {
        int j = f[i - 1];
        while(j && str[j] != str[i - 1]) j = f[j];
        if(str[j] == str[i - 1]) f[i] = j + 1;
        else f[i] = 0;
    }
} 

bool find(char *pat,char *t,int lent,int lenp) {
    int j = 0;
    for(int i = 0;i < lent;i++) {
        while(j && t[i] != pat[j]) j = f[j];
        if(pat[j] == t[i]) j++;
        if(j == lenp) return true;
    }
    return false;
}

int main() {
    int n;
    while(scanf("%d",&n),n) {
        memset(ans,0,sizeof(ans));
        for(int i = 0;i < n;i++) scanf("%s",dict[i]);
        int mlen = strlen(dict[0]);
        int anslen = -1,ansi = 0;
        for(int len = mlen;len >= 1;len--) {
            if(len < anslen) continue;
            for(int pos = 0;pos + len <= mlen;pos++) {
                getfail(dict[0] + pos,len);
                bool ok = true;
                for(int i = 1;i < n;i++) {
                    bool ret = find(dict[0] + pos,dict[i],strlen(dict[i]),len);
                    if(ret == false) {
                        ok = ret; break;
                    }
                }
                if(ok && (len > anslen || (len == anslen && strncmp(ans,dict[0] + pos,len) > 0))) {
                    anslen = len;ansi = pos;
                    strncpy(ans,dict[0] + pos,len);
                    ans[len] = 0;
                }
            }
        }
        if(anslen != -1) {
            puts(ans);
        } else {
            puts("IDENTITY LOST");
        }
    }
    return 0;
}