HDU 1863 畅通工程(Kruskal + 并查集)

题目链接：HDU 1863 畅通工程

Kruskal + 并查集，这题好像没什么好说的。。

#include <iostream>
#include <algorithm>

using namespace std;

const int MAX_M = 100 + 10;
const int MAX_N  = (MAX_M * (MAX_M - 1)) >> 1;
int n,m,ans,sum;
int u[MAX_N],v[MAX_N],w[MAX_N],p[MAX_M],r[MAX_N];

int cmp(int i,int j)
{
    return w[i] < w[j];
}
int _find(int x)
{
    return x == p[x] ? x : (p[x] = _find(p[x]));
}

int main()
{
    while(cin >> n >> m , n)
    {
        ans = 0;
        for(int i = 1;i <= m;i++)
            p[i] = i;
        for(int i = 1;i <= n;i++)
        {
            cin >> u[i] >> v[i] >> w[i];
            r[i] = i;
        }
        sort(r + 1,r + n + 1,cmp);
        int a,b;
        for(int i = 1;i <= n;i++)
        {
            a = _find(u[r[i]]);
            b = _find(v[r[i]]);
            if(a != b)
            {
                p[a] = b;
                m--;
                ans += w[r[i]];
            }
        }
        if(m == 1)
            cout << ans << endl;
        else
            cout << "?" << endl;
    }
    return 0;
}