杭电hdu 3038 how many answers are wrong 并查集求解

http://acm.hdu.edu.cn/showproblem.php?pid=3038

经过网上的搜罗，基本上明白了这个题的意思，网站http://hi.baidu.com/fp_lv/blog/item/a471530a86df7b90d53f7c2c.html讲解的很清楚，我这里只记录下网址和我的代码，以便以后随时查看。

#include <stdio.h>#define MAX 200001int father[MAX];int sum[MAX];//存储从1到i相加的结果int n,m;int ai, bi, si;void init(){for(int i = 0; i <= n; i ++){father[i] = i;sum[i] = 0;}}int getfather(int x){if(x == father[x])return x;int now = getfather(father[x]);//sum[x] += sum[father[x]];//需要我研究的地方father[x] = now;return now;}bool join(int a, int b){int fa = getfather(a);int fb = getfather(b);if(fa == fb)return false;father[fb] = fa;sum[fb] = sum[a] - sum[b] + si;//return true;}int main(){//freopen("input.txt","r",stdin);//freopen("output.txt","w",stdout);while(~scanf("%d%d",&n,&m)){init();int ans = 0;while(m--){scanf("%d%d%d",&ai, &bi, &si);ai --;if(!join(ai, bi)&&sum[bi] - sum[ai] != si)ans ++;}printf("%d\n", ans);}return 0;}