学步园

基础的带权并查集，也是入门的种类并查集，具体做法参考poj 1182 食物链

#include <map>
#include <set>
#include <queue>
#include <stack>
#include <vector>
#include <cmath>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <iostream>
#include <algorithm>

using namespace std;

#define lson l, mid, rt << 1
#define rson mid + 1, r, rt << 1 | 1
#define pi acos(-1.0)
#define eps 1e-8
typedef long long ll;
const int inf = 0x3f3f3f3f;
const int N = 2200;

int n, m;
bool OK;

struct node{
	int fa, re;
}a[N];

void init( )
{
	for( int i = 1; i <= n; ++i )
	{
		a[i].fa = i;
		a[i].re = 0;
	}
	OK = 0;
}

int dfs( int x )
{
	if( x == a[x].fa )
		return x;
	int fa = a[x].fa;
	a[x].fa = dfs( fa );
	a[x].re = ( a[fa].re + a[x].re ) % 2;
	return a[x].fa;
}

void Union( int x, int y )
{
	int xx = dfs( x );
	int yy = dfs( y );
	if( xx == yy )
		return;
	a[xx].fa = yy;
	a[xx].re = ( ( (1 - a[x].re) + a[y].re ) % 2 + a[yy].re ) % 2;
}

int main()
{
	int tot, cas = 0;
	scanf("%d", &tot);
	while( tot-- )
	{
		scanf("%d%d", &n, &m);
		init();
		int u, v;
		while ( m-- )
		{
			scanf("%d%d", &u, &v);
			if( OK )
				continue;
			int uu = dfs( u );
			int vv = dfs( v );
			if( uu == vv )
			{
				if( (a[u].re + a[v].re ) != 1 )
				{
					OK = 1;
				}
			}
			else
			{
				Union( u, v );
			}
		}
		printf("Scenario #%d:\n", ++cas );
		if( OK )
			puts("Suspicious bugs found!");
		else
			puts("No suspicious bugs found!");
		puts("");
	}
	return 0;
}