Two City Scheduling

There are 2N people a company is planning to interview. The cost of flying the i-th person to city A is costs[i][0], and the cost of flying the i-th person to city B is costs[i][1].

Return the minimum cost to fly every person to a city such that exactly N people arrive in each city.

Example 1:

Input: [[10,20],[30,200],[400,50],[30,20]]
Output: 110
Explanation: 
The first person goes to city A for a cost of 10.
The second person goes to city A for a cost of 30.
The third person goes to city B for a cost of 50.
The fourth person goes to city B for a cost of 20.

The total minimum cost is 10 + 30 + 50 + 20 = 110 to have half the people
 interviewing in each city.

Note:

  1. 1 <= costs.length <= 100
  2. It is guaranteed that costs.length is even.
  3. 1 <= costs[i][0], costs[i][1] <= 1000
 class Solution {
    public int twoCitySchedCost(int[][] costs) {
        Arrays.sort(costs, (a, b) -> {
            return (a[0] - a[1]) - (b[0] - b[1]);
        });
       
        int sum = 0;
        for (int i = 0; i < costs.length; ++i) {
            if (i < costs.length / 2) {
                sum += costs[i][0];
            } else {
                sum += costs[i][1];
            }
        }
        return sum;
    }
}


Here, we are doing following steps..,

1)  We need to sort costs based on its differences A cost and B cost. For that while sorting, we are finding cost differences between A and B and based on these differences all costs are sorted.
2) Now, for first half add cost of A and for next half add cost of B to result.

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Comments

  1. I did not understand the snippet:
    Arrays.sort(costs, (a, b) -> {
    return (a[0] - a[1]) - (b[0] - b[1]);
    Can you please explain it?

    ReplyDelete
    Replies
    1. Thanks for asking. If we want to sort array of numbers either use sort() or we can sort using above snippet with a change in return a - b(sort array in ascending order). Likewise same, but here 2D so for sorting we can't use a[0] or a[1] alone, we need both. And based on differences it is sorted. If you still confused just add a print statement above return, then you will find working of it. Please do follow us to receive latest updates instantly. Happy Coding..!!

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