51nod 1535深海探险 并查集/dfs

 

 

 

这题刚开始可能想的复杂了，(想用并查集判断是否有圆,之后Tarjan判断触手)，看了大神的代码,orz，可能对图论的基本概念不是很了解,这个东西叫做环套树

（N==M时成立)

上代码了orz

 

 

 

#include <algorithm>
#include <stdio.h>
#include <stack>
#include <istream>
#include <map>
#include <math.h>
#include<iostream>
#include <queue>
#include <string.h>
#include<set>
#include <cstdio>
using namespace std;
const int maxn = 1e3+5;

//int edge[maxn][maxn];
int fa[maxn];
int N, M;
int fin(int x) {
while (x != fa[x])x = fa[x];
return x;
}
void unite(int x, int y) {
x = fin(x), y = fin(y);
if(x==y)return ;
fa[x] = y;
}
int main() {
cin >> N >> M;
for (int i = 0; i <= N; i++)fa[i] = i;
for (int i = 0; i < M; i++) {
int l, r;
cin >> l >> r;
//edge[l][r] = edge[r][l] = 1;
unite(l, r);
}
if(N!=M){
puts("NO");return 0;
}
int tem = fin(1);
// bool f = 1;
for (int i = 1; i <= N; i++) {
if (tem != fin(i)) {
puts("NO"); return 0;
}
}
//if(m==N)
puts("FHTAGN!");
return 0;
}