HDU ~ 1233 ~ 还是畅通工程 （最小生成树）

思路：最小生成树。。。

//#include<bits/stdc++.h>
#include<iostream>
#include<cstdio>
#include<algorithm>
using namespace std;
const int MAXN = 1005;
const int MAXM = 1005 * 1005;
int n, m, f[MAXN], G[MAXN][MAXN];
struct Edge
{
int u, v, w;
bool operator < (const Edge& A) const
{
return w < A.w;
}
}edge[MAXM];
void init()
{
for (int i = 0; i <= n; i++) f[i] = i;
}
int Find(int x){ return f[x] == x ? x : f[x] = Find(f[x]); }
int kruskal()
{
init();
sort(edge, edge + m);
int ans = 0, cnt = 0;
for (int i = 0; i < m; i++)
{
int u = edge[i].u, v = edge[i].v, w = edge[i].w;
int root1 = Find(u), root2 = Find(v);
if (root1 != root2)
{
f[root1] = root2;
ans += w;
cnt++;
if (cnt == n - 1) break;
}
}
return ans;
}
int main()
{
while (~scanf("%d", &n) && n)
{
m = 0;
for (int i = 0; i < n; i++)
{
for (int j = i + 1; j < n; j++)
{
scanf("%d%d%d", &edge[m].u, &edge[m].v, &edge[m].w);
m++;
}
}
printf("%d\n", kruskal());
}
return 0;
}
/*
3
1 2 1
1 3 2
2 3 4
4
1 2 1
1 3 4
1 4 1
2 3 3
2 4 2
3 4 5
0
*/