Two City Scheduling in C++

Suppose there are 2N persons. A company wants to organize one interview. The cost for flying the i-th person to city A is costs[i][0], and the cost for flying the i-th person to city B is costs[i][1]. We have to find the minimum cost to fly every person to a city, such that N people arrive in every city. So if the given list is [[10, 20], [30, 200], [400, 50], [30, 20]] The output will be 110. So we will send the person P1 to city A with cost 10, Second person to city A with cost 30, third and fourth person to city B with cost 50 and 20 respectively.

To solve this, we will follow these steps −

• n := size of the array
• a := n / 2 and b := n / 2
• Sort the array, and let ans := 0
• for i := 0 to n – 1 −
  • if b = 0 and array[i, 0] <= array[i, 1] and a > 0, then
    • decrease a by 1
    • ans := ans + array[i, 0]
  • else
    • decrease b by 1
    • ans := ans + array[i, 1]
• return ans

Example

Let us see the following implementation to get better understanding −

 Live Demo

#include <bits/stdc++.h>
using namespace std;
class Solution {
   public:
   static bool cmp(vector <int> a, vector <int> b){
      return abs(a[0] - a[1]) > abs(b[0] - b[1]);
   }
   int twoCitySchedCost(vector<vector<int>>& costs) {
      int n = costs.size();
      int a = n/2;
      int b = n/2;
      sort(costs.begin(), costs.end(), cmp);
      int ans = 0;
      for(int i = 0; i < n; i++){
         if(b == 0 || (costs[i][0] <= costs[i][1] && a > 0)){
            a--;
            //cout << a << " " << costs[i][0] << endl;
            ans += costs[i][0];
         } else {
            //cout << costs[i][1] << endl;
            b--;
            ans += costs[i][1];
         }
      }
      return ans;
   }
};
main(){
   Solution ob;
   vector<vector<int>> c = {{10,20},{30,200},{400,50},{30,20}};
   cout << ob.twoCitySchedCost(c);
}

Input

[[10,20],[30,200],[400,50],[30,20]]

Output

110