poj1251 Jungle Roads

poj1251 Jungle Roads

/*
题意：输出最小生成树的权值和。每组数据给出节点个数n，以下n-1行，
开头为起始节点，及与它相连的节点数目m，随后m组数据表示和它相连的节点以及边权值(用c++处理空格和换行符)。
思路：Kruskal。
*/
#include <stdio.h>
#include <iostream>
#include <algorithm>
using namespace std;

#define maxn 30

typedef struct{
int x, y;
int w;
}edge;

edge e[maxn * maxn / 2];
int rank_[maxn], father[maxn], sum;

int cmp(edge a, edge b){  //
return a.w < b.w;
}

void make_set(int x){
father[x] = x;
rank_[x] = 0;
}

int find_set(int x){
return  x != father[x] ? find_set(father[x]) : father[x];
}

void union_set(int x, int y, int w){
if(x == y)  return ;
if(rank_[x] > rank_[y])  father[y] = x;
else{
if(rank_[x] == rank_[y])  rank_[y]++;
father[x] = y;
}
sum += w;  //
}

int main(){
int n, m, k, weight, i, j;
char a, b;

while(scanf("%d", &n) && n){
k = 0, sum = 0;
for(i = 0; i < n - 1; i++){
cin >> a >> m, make_set(a - 'A');
for(j = 0; j < m; j++){
cin >> b >> weight, make_set(b - 'A');
e[k].x = a - 'A', e[k].y = b - 'A';
e[k++].w = weight;
}
}
sort(e, e + k, cmp);
for(i = 0; i < k; i++)  union_set(find_set(e[i].x), find_set(e[i].y), e[i].w);
printf("%d\n", sum);
}

return 0;
}