BZOJ4690 Never Wait for Weights（并查集）

　　带权并查集按秩合并即可维护。

#include<iostream>
#include<cstdio>
#include<cmath>
#include<cstdlib>
#include<cstring>
#include<algorithm>
using namespace std;
#define ll long long
char getc(){char c=getchar();while ((c<'A'||c>'Z')&&(c<'a'||c>'z')) c=getchar();return c;}
int gcd(int n,int m){return m==?n:gcd(m,n%m);}
int read()
{
    int x=,f=;char c=getchar();
    while (c<''||c>'') {if (c=='-') f=-;c=getchar();}
    while (c>=''&&c<='') x=(x<<)+(x<<)+(c^),c=getchar();
    return x*f;
}
#define N 100010
int n,m,fa[N],deep[N],weight[N],len[N];
int find(int x)
{
    if (fa[x]==x) return x;
    int p=find(fa[x]);
    weight[x]=weight[fa[x]]+len[x];
    return p;
}
void merge(int x,int y,int z)
{
    int p=find(x),q=find(y);
    if (p!=q)
    {
        if (deep[p]<deep[q]) swap(p,q),swap(x,y),z=-z;
        fa[q]=p;if (deep[p]==deep[q]) deep[p]++;
        weight[q]=len[q]=weight[x]-weight[y]-z;
    }
}
int main()
{
#ifndef ONLINE_JUDGE
    freopen("bzoj4690.in","r",stdin);
    freopen("bzoj4690.out","w",stdout);
    const char LL[]="%I64d\n";
#else
    const char LL[]="%lld\n";
#endif
    n=read(),m=read();
    while (n)
    {
        for (int i=;i<=n;i++) fa[i]=i,deep[i]=,weight[i]=len[i]=;
        while (m--)
        {
            char c=getchar();
            while (c!='!'&&c!='?') c=getchar();
            if (c=='!')
            {
                int x=read(),y=read(),z=read();
                merge(x,y,z);
            }
            else
            {
                int x=read(),y=read();
                if (find(x)!=find(y)) printf("UNKNOWN\n");
                else printf("%d\n",weight[x]-weight[y]);
            }
        }
        n=read(),m=read();
    }
    return ;
}