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P1546 [USACO3.1]最短网络 Agri-Net(Prim)

思考的鸿毛 2022-04-26 阅读 29
算法

P1546 [USACO3.1]最短网络 Agri-Neticon-default.png?t=M3K6https://www.luogu.com.cn/problem/P1546 

#include <iostream>
#include <cstdio>
#include <string>
#include <algorithm>
#include <vector>
#include <queue>
#include <stack>
#include <cstring>
#include <set>
#include <unordered_map>
#include <cmath>
#include <map>
#include <cctype>
#include <cstdlib>
#include <deque>
typedef long long ll;
typedef unsigned long long ull;
using namespace std;
const int MN = 65005;
const int MAXN = 1000010;
const int INF = 0x3f3f3f3f;
#define IOS ios::sync_with_stdio(false)
#define lowbit(x) ((x)&(-x))


int edge[157][146];
int ans;
int n;
bool vis[MAXN];
int d[MAXN];
typedef pair<int, int> P;
inline void Prim() {
	for (int i = 1; i <= n; i++) {
		d[i] = INF;
	}
	priority_queue<P, vector<P>, greater<P> > que;
	que.push(P(0, 1));
	int nown = 0;
	while (!que.empty() && nown < n) {
		P t = que.top();
		que.pop();
		if (vis[t.second]) {
			continue;
		}
		vis[t.second] = true;
		ans += t.first;
		for (int i = 1; i <= n; i++) {
			if (i == t.second)
				continue;
			if (!vis[i] && edge[t.second][i] < d[i]) {
				d[i] = edge[t.second][i];
				que.push(P(d[i], i));
			}
		}
	}
}

int main() {
	scanf("%d", &n);
	for (int i = 1; i <= n; i++) {
		for (int j = 1; j <= n; j++) {
			scanf("%d", &edge[i][j]);
		}
	}
	Prim();
	printf("%d", ans);
	return 0;
}
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