BZOJ 1202 [HNOI2005]狡猾的商人

Posted 2020-10-24 ws_zzy

题解：加权并查集或差分约束

一开始并查集竟然打错了QWQ

#include<iostream>
#include<cstdio>
#include<cstring>
using namespace std;
const int maxn=100009;

int T;

int n,m;
int father[maxn];
int ky[maxn];
int Getf(int x){
	if(father[x]==x)return x;
	int ff=father[x];
	father[x]=Getf(father[x]);
	ky[x]+=ky[ff];
	return father[x];
}

int main(){
	scanf("%d",&T);
	while(T--){
		int fla=1;
		scanf("%d%d",&n,&m);
		for(int i=0;i<=n;++i)father[i]=i;
		for(int i=0;i<=n;++i)ky[i]=0;
		while(m--){
			int x,y,z;
			scanf("%d%d%d",&x,&y,&z);
			--x;
			if(Getf(x)==Getf(y)){
				if(ky[y]-ky[x]!=z)fla=0;
			}else{
				int fx=Getf(x);
				int fy=Getf(y);
				father[fx]=fy;
				ky[fx]=ky[y]-ky[x]-z;
			}
		}
		if(fla)printf("true\n");
		else printf("false\n");
	}
	return 0;
}