計蒜客-連線問題-Krucal-並查集

題目鏈接

無坑，AC代碼

#include<bits/stdc++.h>

using namespace std;
const int maxn = 105;
const int inf = 0x3f3f3f3f;
struct point{
	int x, y;
	point(){
	}
	point(int xx, int yy){
		x = xx;
		y = yy;
	}
};
struct edge{
	int u, v;
	double w;
	edge(){
	}
	edge(int uu, int vv, double ww){
		u = uu, v = vv, w = ww;
	}
	bool operator < (const edge a) const{
		return w > a.w;
	}
};
priority_queue<edge>que;
vector<point>arr;
int n, cnt, fa[maxn];
double ans;

void init(){
	cnt = n;
	ans = 0;
	for(int i = 1; i <= n; i++)
		fa[i] = i;
}

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

bool sam(int a, int b){
	if(getf(a) == getf(b))
		return true;
	return false;
}

void merge(int a, int b){
	if(sam(a, b))
		return ;
	fa[getf(a)] = getf(b);
}

double dis(point a, point b){
	return sqrt((a.x - b.x)*(a.x - b.x) + (a.y - b.y)*(a.y - b.y));
}

int main(){
	cin>>n;
	init();
	for(int i = 0; i < n; i++){
		point temp;
		scanf("%d%d", &temp.x, &temp.y);
		arr.push_back(temp);
		for(int j = 0; j < arr.size(); j++)
			que.push(edge(i, j, dis(arr[i], arr[j])));
	}
	while(cnt != 1){
		edge temp = que.top();
		que.pop();
		if(!sam(temp.u, temp.v)){
			merge(temp.u, temp.v);
			cnt--;
			ans += temp.w;
		}
	}
	printf("%.2f\n", ans);
	return 0;
}