Prim's algorithm implementation for minimum spanning tree.

Minimum spanning tree-prim .cpp

#include<bits/stdc++.h>
using namespace std;
#define mx 50005
typedef pair<long long int,int> PII;
vector<PII>g[mx];
bool marked[mx];
long long prim(int x)
{
    priority_queue<PII, vector<PII>, greater<PII> > Q;
    int y;
    long long minimumCost = 0;
    PII p;
    Q.push(make_pair(0, x));
    while(!Q.empty())
    {
        
        p = Q.top();
        Q.pop();
        x = p.second;
        // Checking for cycle
        if(marked[x] == true)
            continue;
        minimumCost += p.first;
        marked[x] = true;
        for(int i = 0; i < g[x].size(); ++i)
        {
            y = g[x][i].second;
            if(marked[y] == false)
                Q.push(g[x][i]);
        }
    }
    return minimumCost;
}

int main()
{
   
        int n,m;
        scanf("%d%d",&n,&m);
 
        int x,y;
        long long w;
        for(int i=0;i<m;i++){
            scanf("%d%d%lld",&x,&y,&w);
        
            g[x].push_back(make_pair(w,y));
            g[y].push_back(make_pair(w,x));
          
        }
        long long  int lowcost=prim(1);
        printf("%lld",lowcost);
        
        
 
    
}