Prims Algo. minimum spaning tree

#include <bits/stdc++.h>
using namespace std;
int spanningTree(int V, int E, vector<vector<int>> &graph);
// Driver code

int main() {
    int t;
    cin >> t;
    while (t--) {
        int V, E;
        cin >> V >> E;
        vector<vector<int> > graph(V, vector<int>(V, 0));
        int i=0;
        while (i++<E) {
            int u, v, w;
            cin >> u >> v >> w;
            u--, v--;
            graph[u][v] = w;
            graph[v][u] = w;
        }

        cout << spanningTree(V, E, graph) << endl;
    }
    return 0;
}
// } Driver Code Ends

typedef pair<int, int> PII;
// Function to construct and print MST for
// a graph represented using adjacency
// matrix representation, with V vertices.
// graph[i][j] = weight if edge exits else INT_MAX
bool visited[1000+1];

int prim(vector<PII> adj[]){
    priority_queue<PII, vector<PII>, greater<PII> > pq;
    int minCost = 0;
    PII p;
    pq.push({0,1});
    while(!pq.empty())
    {
        p=pq.top();
        pq.pop();
        int x = p.second;
        if(visited[x])
            continue;
        minCost += p.first;
        visited[x] = true;
        for(int i=0; i<adj[x].size(); i++)
        {
            int y = adj[x][i].second;
            if(!visited[y])
                pq.push(adj[x][i]);
        }
    }
    return minCost;
}

int spanningTree(int V, int E, vector<vector<int>> &graph) {
    // code here

    for(int i=0; i<=V; i++)
        visited[i] = 0;
    vector<PII> adj[V+1];

    for(int i=0; i<V; i++)
    {
        for(int j=i; j<V; j++)
        {
            if(graph[i][j] != 0)
            {

                adj[i+1].push_back(make_pair(graph[i][j],j+1));
                adj[j+1].push_back(make_pair(graph[i][j],i+1));
            }
        }
    }
    return prim(adj);
}