洛谷 P1195.口袋的天空

题目链接：https://www.luogu.com.cn/problem/P1195

今天上算法设计课，复习一下 Kruskal 和并查集。

---

 

放AC代码

#include<bits/stdc++.h>
using namespace std;
int n, m, k, ans;
int p[1010];

struct node
{
    int u, v, w;
}edge[10010];

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

int getParent(int o)
{
    return o == p[o] ? o : getParent(p[o]);
}

int main()
{
    cin >> n >> m >> k;
    for(int i = 1; i <= m; i ++)
    {
        int x, y, z;
        cin >> x >> y >> z;
        edge[i].u = x;
        edge[i].v = y;
        edge[i].w = z;
    }

    for(int i = 1; i <= n ; i ++)
        p[i] = i;

    sort(edge + 1, edge + 1 + m, cmp);

    int h = 1;//记录到底几个节点
    int js = 1; //计数已经加入几条边
    while(js <= n - k) //k个树需要n-k条边
    {
        if(h > m)
        {
            cout << "No Answer" << endl;
            return 0;
        }
        int x = edge[h].u, y = edge[h].v, w = edge[h].w;
        int fx = getParent(x), fy = getParent(y);
        if(fx != fy)
        {
            js ++;
            p[fx] = fy;
            ans += w;
        }
        h ++;
    }

    if(js)  cout << ans;
    return 0;
}