hdu 1181（传递闭包)

题目：hdu 1181 变形果

题意：给一些边，求传递闭包中B->M是否为真。

题解：第一个传递闭包，很裸。

代码：

#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <cmath>
#include <iostream>
#include <algorithm>
#include <queue>
#include <stack>
#include <vector>
#include <deque>
#include <set>
#include <map>
#include <string>
using namespace std;
#define For(i,a) for(i=0;i<a;i++)
#define Foru(i,a,b) for(i=a;i<=b;i++)
#define Ford(i,a,b) for(i=a;i>=b;i--)
#define clr(ar,vel) memset(ar,vel,sizeof(ar))
#define PB push_back
typedef long long ll;
const int maxint = 0x7fffffff;
const ll maxll = 1LL<<60;
int g[30][30];
string s;
int main(){
	#ifndef in
	ios::sync_with_stdio(false);
	#endif
	int from, to;
	while(cin >> s){
		memset(g, 0, sizeof(g));
		if( s == "0" ) break;
		from = s[0] - 'a';
		to = s[s.length()-1] - 'a';
		g[from][to] = 1;
		while(cin >> s){
			if( s == "0" ) break;
			from = s[0] - 'a';
			to = s[s.length()-1] - 'a';
			g[from][to] = 1;
		}
		for(int k = 0; k < 26; k ++){
			for(int i = 0; i < 26; i ++){
				for(int j = 0; j < 26; j ++){
					g[i][j] = g[i][j] | (g[i][k]&g[k][j]);
				}
			}
		}
		from = 'b' - 'a';
		to = 'm' - 'a';
		if( g[from][to] ) cout << "Yes." << endl;
		else cout << "No." << endl;
	}
	return 0;
}