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Discussion of Problem 1982. Electrification Plan

What is wrong in this?
Posted by Aditya Singh 4 Jan 2018 04:11
#include <stdio.h>
#include <iostream>
#include <limits>
#include <cstdint>
#include <cmath>
#include <cstdlib>
#include <algorithm>
#include <vector>
#include <array>
#include <string.h>
#include <stack>
#include <queue>
#include <stdint.h>
#include <sstream>
#include <map>
#include <set>
#define mem(x, y) memset(x, y, sizeof x);
#define __STDC_LIMIT_MACROS
typedef long long ll;
using namespace std;

struct Edge{
    int s,d,w;
    Edge(){
        this->s = this->d = this->w = NULL;
    }
    Edge(int s, int d, int w){
        this->s = s;
        this->d = d;
        this->w = w;
    }
};

bool myComp(struct Edge a, struct Edge b){
    return a.w<b.w;
}

int mfind(int parent[], int u){
    if(parent[u]==-1){
        return u;
    }

    parent[u] = mfind(parent,parent[u]);

    return parent[u];
}

void Union(int parent[], int rank[], int u, int v){
    int x = mfind(parent,u);
    int y = mfind(parent,v);

    if(rank[x]<rank[y]){
        parent[x] = y;
    }
    else if(rank[y]< rank[x]){
        parent[y] = x;
    }
    else{
        parent[x] = y;
        rank[y]++;
    }
}

int main() {

    vector<Edge> edges;
    int n,k,tot=0;
    cin >> n >> k;
    int check[n];
    mem(check,0);
    for(int i=0; i<k; i++){
        int x;
        cin >> x;
        check[x-1] = 1;
    }

    for(int i=0; i<n; i++){
        for(int j=0; j<n; j++){
            int inp;
            cin >> inp;
            if(i>j){
                struct Edge ed(i,j,inp);
                edges.push_back(ed);
            }
        }
    }

    sort(edges.begin(), edges.end(), myComp);

    // KRUSKAL MST
    int parent[n], rank[n];
    mem(parent,-1);
    mem(rank,0);
    int e=0;

    while(e<n-1){
        struct Edge next_edge = edges[e++];

        int x = mfind(parent, next_edge.s);
        int y = mfind(parent, next_edge.d);

        if(x!=y){
            tot+=next_edge.w;
            if(check[next_edge.s]==1 && check[next_edge.d]==1) tot-=next_edge.w;
            e++;
            Union(parent,rank,x,y);
        }

    }

    cout << tot << endl;

    return 0;


}