UVALive 6187 Never Wait for Weights 带权并查集

//meek
#include <iostream>
#include <cstdio>
#include <cmath>
#include <string>
#include <cstring>
#include <algorithm>
#include <queue>
#include <map>
#include <set>
#include <stack>
#include <sstream>
#include <vector>
using namespace std ;
typedef long long ll;
#define mem(a) memset(a,0,sizeof(a))
#define pb push_back
#define fi first
#define se second
#define MP make_pair
inline ll read()
{
    ll x=0,f=1;
    char ch=getchar();
    while(ch<‘0‘||ch>‘9‘)
    {
        if(ch==‘-‘)f=-1;
        ch=getchar();
    }
    while(ch>=‘0‘&&ch<=‘9‘)
    {
        x=x*10+ch-‘0‘;
        ch=getchar();
    }
    return x*f;
}
//****************************************

const int N=500000+100;
const ll inf = 1ll<<61;
const int mod= 1000000007;

char ch[20];
int d[N],parent[N],flag,n;
ll ans;
void init () {
    for(int i=0;i<=n;i++) parent[i]=i;
    mem(d);
}
int finds(int x){
   if(x==parent[x])return x;
   int fy=finds(parent[x]);
   d[x] = d[parent[x]] + d[x];
   return  parent[x]=finds(parent[x]);
 }
int main() {
    int a,b,m,w;
    while(scanf("%d%d",&n,&m)!=EOF) {
        if( n==0 &&m==0) break;
        init();
        for(int i=1;i<=m;i++) {
            scanf("%s",ch);
            if(ch[0]==‘!‘) {
                scanf("%d%d%d",&a,&b,&w);
                 int fx=finds(a);
                int fy=finds(b);
                if(fx!=fy) parent[fy]=fx,d[fy]=d[a]-w-d[b];
            }
            else {
                scanf("%d%d",&a,&b);
                int fx=finds(a);
                int fy=finds(b);
                if(fx==fy) {
                   cout<<d[a]-d[b]<<endl;
                }
                else {
                    printf("UNKNOWN\n");
                }
            }
        }
    }
    return 0;
}