并查集(路径更新) LA 3027 Corporative Network

 

题目传送门

题意:训练指南P192

分析:主要就是一个在路径压缩的过程中,更新点i到根的距离

#include <bits/stdc++.h>
using namespace std;

const int N = 2e4 + 5;
struct DSU	{
	int rt[N], d[N];
	void init(void)	{
		memset (rt, -1, sizeof (rt));
		memset (d, 0, sizeof (d));
	}
	int Find(int x)	{
		if (rt[x] != -1)	{
			int root = Find (rt[x]);	//先找到根
			d[x] += d[rt[x]];			//回溯的过程把距离更新
			return rt[x] = root;		//路径压缩
		}
		else	return x;
	}
	void Union(int x, int y)	{
		if (x == y)	{
			d[x] = 0;	return ;
		}
		else	{
			rt[x] = y;
			d[x] = abs (x - y) % 1000;
		}
	}
	bool same(int x, int y)	{
		return Find (x) == Find (y);
	}
}dsu;

int main(void)	{
	int T;	scanf ("%d", &T);
	while (T--)	{
		int n;	scanf ("%d", &n);
		char str[3];	dsu.init ();
		int x, y;
		while (scanf ("%s", str) == 1)	{
			if (str[0] == 'O')	break;
			if (str[0] == 'E')	{
				scanf ("%d", &x);
				dsu.Find (x);
				printf ("%d\n", dsu.d[x]);
			}
			else	{
				scanf ("%d%d", &x, &y);
				dsu.Union (x, y);			//初始就是到fa的距离
			}
		}
	}

	return 0;
}