HDU 3038 带权并查集

可以清晰看出val - dist[y] + dist[x] 就是yy到祖先的距离dist[yy]

#include <iostream>#include <cstdio>#include <string.h>using namespace std;const int AX = 2e5+666;const int MAXN = 4e4+666;int pre[AX];int dist[AX];int ans ;int n,m;void init(){for( int i = 1 ; i <= n ; i++ ){pre[i] = i;dist[i] = 0;}}int find(int x){if( x!= pre[x] ){int t = pre[x];pre[x] = find(pre[x]);dist[x] += dist[t];          //压缩路径时多出的更新操作} return pre[x];}void mix(int x,int y,int val){int xx = find(x);int yy = find(y);if( xx != yy ){pre[yy] = xx ;dist[yy] = val - dist[y] + dist[x];         //这一步的理解在开头给出}else{if( dist[yy] != val - dist[y] + dist[x] ) ans++;}}int main(){while(~scanf("%d%d",&n,&m)){ans = 0;init();int x,y,val;while( m-- ){scanf("%d%d%d",&x,&y,&val);mix(x-1,y,val);}printf("%d\n",ans);}return 0;}