HDU4324——DFS——Triangle LOVE

http://acm.hdu.edu.cn/showproblem.php?pid=4324

/*
搜索一个三角形，用vector+vis来减少复杂度
*/
/************************************************
* Author        :Powatr
* Created Time  :2015-8-25 10:42:01
* File Name     :E.cpp
 ************************************************/

#include <cstdio>
#include <algorithm>
#include <iostream>
#include <sstream>
#include <cstring>
#include <cmath>
#include <string>
#include <vector>
#include <queue>
#include <deque>
#include <stack>
#include <list>
#include <map>
#include <set>
#include <bitset>
#include <cstdlib>
#include <ctime>
using namespace std;

#define lson l, mid, rt << 1
#define rson mid + 1, r, rt << 1 | 1
typedef long long ll;
const int MAXN = 2000 + 10;
const int INF = 0x3f3f3f3f;
const int MOD = 1e9 + 7;

char  mp[MAXN][MAXN];
int vis[MAXN][MAXN];
int n;
vector<int> G[MAXN];
bool dfs(int x, int y, int step, int ex, int ey)
{
    if(step == 2 && y == ex) return true;
    if(vis[x][y]) return false;
    vis[x][y] = 1;
    if(step >= 2) return false;
    for(int i = 0; i < G[y].size(); i++){
        int v = G[y][i];
       // printf("%d %d\n", y, v);
           if(!dfs(y, v, step + 1, ex, ey));
           else return true;
    }
    return false;
}

bool solve()
{
    for(int i = 1; i <= n; i++)
        for(int j = 0; j < G[i].size(); j++){
            int v = G[i][j];
            if(!vis[i][v])
                if(dfs(i, v, 0, i, v)){
                    return true;
                }
            }
    return false;
}

int main(){
    int T;
    scanf("%d", &T);
    for(int cas = 1; cas <= T; cas++){
        memset(vis, 0, sizeof(vis));
        scanf("%d", &n);
        for(int i = 0; i <= n; i++)
            G[i].clear();
        for(int i = 1; i <= n; i++)
            scanf("%s", mp[i] + 1);
        for(int i = 1; i <= n; i++){
            for(int j = 1; j <= n; j++){
                if(mp[i][j] == ‘1‘){
                    G[i].push_back(j);
                }
            }
        }
        printf("Case #%d: ", cas);
        if(solve()) puts("Yes");
        else puts("No");
    }
    return 0;
}