【HDU】How Many Answers Are Wrong（带权并查集）

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num[i]代表i到根节点的值

这道题一开始竟然以为是线段树= =！后来发现线段树无法进行子区间的维护

#include<cstdio>
#include<cstring>
#include<algorithm>
using namespace std;
const int maxn = 222222;
int fa[maxn],num[maxn];
int find_father(int u){
    if(fa[u] == u)
        return fa[u];
    else{
        int temp  = fa[u];
        fa[u] = find_father(fa[u]);
        num[u] += num[temp];
        return fa[u];
    }
}
int main(){
    int n,m;
    while(scanf("%d%d",&n,&m) != EOF){
        memset(num,0,sizeof(num));
        int cnt = 0;
        for(int i = 0; i <= n; i++) fa[i] = i;
        for(int i = 0; i < m; i++){
            int x,y,z;
            scanf("%d%d%d",&x,&y,&z);
            x --;
            int l = find_father(x),r = find_father(y);
            if(l == r){
                int e = num[y] - num[x];
                if(e != z){
                    cnt ++;
                }
            }
            else{
                fa[r] = l;
                num[r] = z + num[x] - num[y];
            }
        }
        printf("%d\n",cnt);
    }
    return 0;
}

【HDU】How Many Answers Are Wrong（带权并查集）

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原文地址：http://blog.csdn.net/u013451221/article/details/45486865