[BZOJ1116] CLO

1116: [POI2008]CLO

Time Limit: 10 Sec  Memory Limit: 162 MB
Submit: 1311  Solved: 709
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Description

Byteotia城市有n个 towns m条双向roads. 每条 road 连接 两个不同的 towns ,没有重复的road. 你要把其中一些road变成单向边使得：每个town都有且只有一个入度

Input

第一行输入n m.1 <= n<= 100000,1 <= m <= 200000 下面M行用于描述M条边.

Output

TAK或者NIE 常做POI的同学,应该知道这两个单词的了...

Sample Input

4 5
1 2
2 3
1 3
3 4
1 4

Sample Output

TAK

上图给出了一种连接方式.

 

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没有环输出NIE，并查集水过去

 

---

#include <iostream>
#include <cstdio>
using namespace std;
int n, m;
int fa[];
int Find(int x){return x==fa[x]?x:fa[x]=Find(fa[x]);}
bool mark[];
int main()
{
    scanf("%d%d", &n, &m);
    for (register int i =  ;i <= n ;i ++)fa[i] = i;
    for (register int i =  ; i <= m ; i ++)
    {
        int x, y;
        scanf("%d%d", &x, &y);
        int fx = Find(x), fy = Find(y);
        if (fx == fy) mark[fx] = ;
        else fa[fx] = fy, mark[fy] = (mark[fx] | mark[fy]);
    }
    for (register int i =  ; i <= n ; i ++){
        if (mark[Find(i)] == ) return puts("NIE"), ;
    }
    puts("TAK");
    return ;
}