hdu 1863 畅通工程

#include <stdio.h>#include <stdlib.h> #include <string.h>typedef struct{int a,b;int cost;int status; }Edge;Edge input[5050];int cost[5050];int parent[5050];int cmp(const void  *a,const void  *b){return (((Edge *)a)->cost - ((Edge *)b)->cost);} int root(int n){if(parent[n] == 0) return n;else return  parent[n] = root(parent[n]);} int  kruskal(int N){int a_root,b_root;int sum = 0;for(int i = 0; i < N;++i){a_root = root(input[i].a);b_root = root(input[i].b);if( a_root != b_root){a_root < b_root?parent[b_root] = a_root:parent[a_root] = b_root;sum += input[i].cost;}} return sum;}int main(int argc, char *argv[]){//FILE *fp;//fp = freopen("in1.txt","r",stdin);int N,sum,M;int flag = 1;while(scanf("%d",&N),N){scanf("%d\n",&M);flag = 1;for(int i = 0;i < N;++i){scanf("%d%d%d",&input[i].a,&input[i].b,&input[i].cost);}memset(parent,0,sizeof(parent));qsort(input,N,sizeof(Edge),cmp);sum = kruskal(N);for(int i = 2; i <= M;++i){if(parent[i] == 0){printf("?\n");flag = 0;break;}}if(flag)printf("%d\n",sum);}return 0;}