[C++] Prim Algorithm with Priority Queue

#include <cstdio>
#include <vector>
#include <queue>
#define INF 987654321
using namespace std;

vector<vector<pair<int, int>>> graph;
int V, E;

int prim() {
	vector<int> cost(V + 1, INF);
	vector<int> prev(V + 1, -1);
	vector<bool> visit(V + 1, false);
	priority_queue<pair<int, int>, vector<pair<int, int>>, greater<>> pq;
	
	pq.push(make_pair(0, 1));
	cost[1] = 0;

	while (!pq.empty()) {
		int u = pq.top().second;
		pq.pop();

		visit[u] = true;
		for (auto next : graph[u]) {
			int v = next.second;
			int weight = next.first;

			if (!visit[v] && cost[v] > weight) {
				cost[v] = weight;
				pq.push(make_pair(cost[v], v));
				prev[v] = u;
			}
		}
	}

	int sum = 0;
	for (int i = 1; i <= V; i++)
		sum += cost[i];
	return sum;
}

int main() {
	scanf("%d%d", &V, &E);
	graph.assign(V + 1, vector<pair<int, int>>());

	for (int i = 0, u, v, w; i < E; i++) {
		scanf("%d%d%d", &u, &v, &w);
		graph[u].push_back(make_pair(w, v));
		graph[v].push_back(make_pair(w, u));
	}

	printf("%d", prim());
	return 0;
}