hdu 1869赤裸裸的最短路

/*
 * hdu1869/win.cpp
 * Created on: 2012-7-31
 * Author    : ben
 */
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <cmath>
#include <ctime>
#include <iostream>
#include <algorithm>
#include <queue>
#include <set>
#include <stack>
#include <string>
#include <vector>
#include <deque>
#include <list>
#include <functional>
#include <numeric>
#include <cctype>
using namespace std;

const int SIZE = 105;
const int MAX = 0x7fffffff;
int mymap[SIZE][SIZE], N;
void init() {
    int i, j;
    for (i = 0; i < N; i++) {
        for (j = 0; j < N; j++) {
            mymap[i][j] = MAX;
        }
    }
}
void Floyd() {
    int i, j, k;
    for (k = 0; k < N; k++) {
        for (i = 0; i < N; i++) {
            for (j = 0; j < N; j++) {
                if(mymap[i][k] < mymap[i][j] - mymap[k][j]) {
                    mymap[i][j] = mymap[i][k] + mymap[k][j];
                }
            }
        }
    }
}
int main() {
#ifndef ONLINE_JUDGE
    freopen("data.in", "r", stdin);
#endif
    int M, a, b;
    while(scanf("%d%d", &N, &M) == 2) {
        init();
        for(int i = 0; i < M; i++) {
            scanf("%d%d", &a, &b);
            mymap[a][b] = mymap[b][a] = 1;
        }
        Floyd();
        bool flag = true;
        for(int i = 0; i < N; i++) {
            for(int j = i + 1; j < N; j++) {
                if(mymap[i][j] > 7) {
                    flag = false;
                }
            }
        }
        puts(flag ? "Yes" : "No");
    }
    return 0;
}