BZOJ4690: Never Wait for Weights

裸带权并查集。

#include<cstdio>
#define N 100005
int m,i,j,s,t,u,d[N],p[N];
char k;
int find(int i){
	if(p[i]^i&&find(p[i]))
		d[i]+=d[p[i]];
	return p[i]=p[p[i]];
}
int main(){
	while(scanf("%d%d",&s,&m)&&s){
		for(;s;--s)
			d[p[s]=s]=0;
		while(m--){
			scanf(" %c%d%d",&k,&s,&t);
			i=find(s),j=find(t);
			if(k=='!'){
				scanf("%d",&u);
				p[i]=j;
				d[i]=d[t]+u-d[s];
			}else if(i^j)
				puts("UNKNOWN");
			else
				printf("%d\n",d[s]-d[t]);
		}
	}
}