代码:
10 10 1 2 150 3 4 200 1 5 270 2 6 200 6 5 80 4 7 150 8 9 100 4 8 50 1 7 100 9 2 100
2 <div style='font-family:Times New Roman;font-size:14px;background-color:F4FBFF;border:#B7CBFF 1px dashed;padding:6px'><div style='font-family:Arial;font-weight:bold;color:#7CA9ED;border-bottom:#B7CBFF 1px dashed'><i>Hint</i></div> Hint: (PS: the 5th and 10th requests are incorrect) </div>
思路:
用带权并查集做
合并这a1,a2两棵树 a1,a2之间的相对距离,可以得到rank[root_a] = rank[a1]+x-rank[a2]
代码:
#include<cstdio>
#include<cmath>
using namespace std;
#define N 50005
int f[N], rank[N], n, m;
void init(){
for(int i=0; i<=n; ++i)
f[i]=i, rank[i]=0;
}
int find(int x){
if(x==f[x]) return f[x];
int t=f[x];
f[x] = find(f[x]);
rank[x] += rank[t];
return f[x];
}
bool Union(int x,int y, int m){
int a=find(x), b=find(y);
if(a==b){
if(rank[x]+m!=rank[y])
return false;
return true;
}
f[b] = a;
rank[b] = rank[x]+m-rank[y];
return true;
}
int main(){
int a,b,x;
while(~scanf("%d%d",&n,&m)){
init();
int cnt=0;
for(int i=0; i<m; ++i){
scanf("%d%d%d",&a,&b,&x);
if(!Union(a, b, x)){
++cnt;
}
}
printf("%d\n",cnt);
}
return 0;
}