并查集Find函数

void Find(int x){
    if(pre[x] != x) pre[x] = Find(pre[x]);
    return pre[x];
}


int Find(int x){
    int p, tmp;
    p = x;
    while(x != pre[x]){
        x = pre[x];
    }
    while(p != x){
        tmp = pre[p];
        pre[p] = x;
        p = tmp;
    }
    return x;
}

并查集的应用有很多这里给大家推荐一道很好的题。http://120.78.128.11/Problem.jsp?pid=2144

这道题的代码如下：

int pre[maxn], maxx[maxn], num[maxn]; 
int Find(int x){
	int p, tmp;
	p = x;
	while(x != pre[x]){
		x = pre[x];
	}
	while(p != x){
		tmp = pre[p];
		pre[p] = x;
		p = tmp;
	}
	return x;
}
void join(int x, int y){
	int p, q;
	p = Find(x);
	q = Find(y);
	if(p != q){
		pre[p] = q;
		maxx[q] = max(maxx[p], maxx[q]);
		num[q] += num[p];
	} 
}

int main(){
	int n, m;
	char str[10];
	while(~scanf("%d%d",&n, &m)){
		for(int i = 1; i <= n; i++){
			pre[i] = i; 
			num[i] = 1;
			maxx[i] = i;
		}
		int Set = n;
		while(m--){
			getchar();
			int x, y;
			scanf("%s",str);
			if(str[0] == 'u'){
				scanf("%d%d",&x, &y);
				if(Find(x) != Find(y)){
					join(x,y);
					Set--;
				}
			}
			else if(str[0] == 's' && str[1] == 'a'){
				scanf("%d%d",&x, &y);
				if(Find(x) == Find(y)) puts("1");
				else puts("0");
			}
			else if(str[0] == 'n'){
				scanf("%d",&x);
				printf("%d\n",num[Find(x)]);
			}
			else if(str[0] == 'm'){
				scanf("%d", &x);
				printf("%d\n", maxx[Find(x)]);
			}else{
				printf("%d\n",Set);
			}
		}
	}
	return 0;
}

这个题就很好的展示了并查集的一些基本操作。