HDU 2818 && POJ1988 带权并查集

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Description

John are playing with blocks. There are N blocks (1 <= N <= 30000) numbered 1...N。Initially, there are N piles, and each pile contains one block. Then John do some operations P times (1 <= P <= 1000000). There are two kinds of operation:

M X Y : Put the whole pile containing block X up to the pile containing Y. If X and Y are in the same pile, just ignore this command.
C X : Count the number of blocks under block X

You are request to find out the output for each C operation.

Input

The first line contains integer P. Then P lines follow, each of which contain an operation describe above.

Output

Output the count for each C operations in one line.

Sample Input

6M 1 6C 1M 2 4M 2 6C 3C 4

Sample Output

今天打比赛前写的一道带权并查集

题意搬砖头把包含有 a的砖头堆里的所有砖头转移到包含b的砖头堆上问 K砖头下有几块砖头

思路：并查集额外开两个数组一个记录这堆砖头堆的砖头高度另一个记录k砖头下有几块砖头每次合并的时候更新砖头高度和被合并的砖头堆最底下砖头下面有几块砖头用户find 时更新

ac code

#include <iostream>#include <cstdio>#include <cstring>#include <cmath>#include <queue>#include <algorithm>#include <cstdlib>using namespace std;const int maxn=30005;int root[maxn],under[maxn],height[maxn];void init(int n){    for(int i=0;i<=n;i++)        root[i]=i,under[i]=0,height[i]=1;}int fin(int x){    if(root[x]==x) return x;    int rot=root[x];    root[x]=fin(root[x]);    under[x]+=under[rot];//递归更新要查找的点    return root[x];}void Union(int u,int v){    int ru=fin(u);    int rv=fin(v);    if(ru==rv) return;    root[ru]=rv;//ru堆的最底下变成了rv    under[ru]=height[rv];//ru砖头下有rv块砖头    height[rv]+=height[ru];//更新rv堆砖头高度}int main(){    char ch[5];    int u,v,n;    while(scanf("%d",&n)!=EOF)    {        init(n<30000?n:30000);        for(int i=0;i<n;i++)        {            scanf("%s",ch);            if(ch[0]=='M')            {                scanf("%d%d",&u,&v);                Union(u,v);            }            else            {                scanf("%d",&u);                fin(u);//这里必须有   因为算法是延迟更新的    这里如果不查找   就不会更新                printf("%d\n",under[u]);            }        }    }    return 0;}

现在也找不到什么带权并查集的题了也就发了两篇博客总的来说带权并查集的核心在于延迟更新

建图的时候理清楚合并的集合的关系就好办了

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