题解【洛谷P1995】口袋的天空

题面

题解

从图中删边，直到图中只剩\(k\)条边，计算权值之和即可。

代码

#include <iostream>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <algorithm>
#include <cmath>
#include <cctype>
#define gI gi
#define itn int
#define File(x) freopen(x".in","r",stdin);freopen(x".out","w",stdout)

using namespace std;

inline int gi()
{
    int f = 1, x = 0; char c = getchar();
    while (c < '0' || c > '9') {if (c == '-') f = -1; c = getchar();}
    while (c >= '0' && c <= '9') {x = x * 10 + c - '0'; c = getchar();}
    return f * x;
}

int n, m, k, tot, ans, sum, fa[1003];
struct OrzAncer
{
	int x, y, l;
} a[10003];

int getf(int u)
{
	if (fa[u] == u) return u;
	return fa[u] = getf(fa[u]);
}

inline bool cmp(OrzAncer X, OrzAncer Y) {return X.l < Y.l;}

int main()
{
	//File("P1195");
	n = gi(), m = gi(), k = gi();
	for (int i = 1; i <= m; i+=1)
	{
		a[i].x = gi(), a[i].y = gi(), a[i].l = gi();
	}
	for (int i = 1; i <= n; i+=1) fa[i] = i;
	sort(a + 1, a + 1 + m, cmp);
	tot = n;
	bool fl = true;
	for (int i = 1; i <= m; i+=1)
	{
		int u = getf(a[i].x), v = getf(a[i].y);
		if (u != v)
		{
			fa[u] = v;
			--tot;//删边
			ans = ans + a[i].l;
			if (tot == k) {fl = false; break;}//删完了
		}
	}
	if (fl) puts("No Answer");
	else printf("%d\n", ans);
	return 0;
}