克鲁斯卡尔算法模版

#define MAX 25005
typedef struct edge
{
	int x, y;
	int w;
}edge;

edge e[MAX];
int father[MAX], ranks[MAX];

bool cmp(edge a,edge b)
{
	return a.w < b.w;
}

void Make_Set(int n)
{
	for(int i = 1; i <= n; i++)
	{
		father[i] = i;
		ranks[i] = 0;
	}
}

int Find_Set(int x)
{
	if(x != father[x])
		father[x] = Find_Set(father[x]);
	return father[x];
}

void Merge_Set(int x, int y)
{
	x = Find_Set(x);
	y = Find_Set(y);
	if(x == y) return;
	if(ranks[x] > ranks[y])
	{
		father[y] = x;
	}
	else if(ranks[x] < ranks[y])
	{
		father[x] = y;
	}
	else 
	{
		ranks[y]++;
		father[x] = y;
	}
}

思想：贪心选择最小的w值，其他的就是并查集的利用了。