Blue Jeans POJ - 3080

#include<iostream>
#include<cstdio>
#include<string.h>
#include<cmath>
#include<cstdlib>

using namespace std;

const int N = 1e3+5;

int nxt[N];
int cnt = 0;
string s[15];

void GetNext(string s, int length) {
	int i=0, j=-1;

	nxt[0] = -1;//必须有...

	while(i < length) {
		if(j == -1 || s[i] == s[j]) {
			i++;
			j++;
			nxt[i] = j;
		} else j = nxt[j];
	}
}

int KMP(string s1, int n, string s2, int m) {
	int i = 0, j = 0;

	while(i < n) {
		if(j == -1 || s1[i] == s2[j]) {
			i++;
			j++;
		} else
			j = nxt[j];

		if(j == m) {
//			cout<<s2 << i-j+1 << endl;
			return i-j+1;
		}
	}
	return -1;
}

int main() {
	int T;

	cin >> T;

	while(T--) {
		int n, m;

		cin >> n;

		for(int i=0; i<n; i++) {
			cin >> s[i];
		}
		string ans = "Z";
		
		int i, j, k, len = s[0].length();
		
		for(i=3; i<=len; i++)
			for(int j =0; j<=len-i; j++) {

				string s2 = s[0].substr(j, i);
		//		cout << s2.length() << " " << i << endl;
				memset(nxt, 0, sizeof(nxt));
				GetNext(s2, i);
		
				for(k=1; k<n; k++) {
					int tn = s[k].length();
					
	
					if(tn < i || KMP(s[k], tn, s2, i) ==-1) {
						break;
					}
				}
				if(k == n) {	
					if(ans.size() < s2.size()) {
						ans = s2;
					} else if(ans.size() == s2.size() && strcmp(ans.c_str(), s2.c_str()) > 0) {
						ans = s2;
					}
				}
			}

		if(ans.size()<3)
			cout << "no significant commonalities" << endl;
		else
			cout << ans << endl;

	}

	return 0;

}