Maximize happiness of selected children

Array Greedy Sorting

58.7% acceptance

Feb 25, 2026

937

You are given an array happiness of length n, and a positive integer k. There are n children standing in a queue, where the ith child has happiness value happiness[i]. You want to select k children from these n children in k turns. In each turn, when you select a child, the happiness value of all the children that have not been selected till now decreases by 1. Note that the happiness value cannot become negative and gets decremented only if it is positive. Return the maximum sum of the happiness values of the selected children you can achieve by selecting k children.

Solution

Rust

Time O(n)

Space O(1)

LeetCode

solution.rs

impl Solution {
  pub fn maximum_happiness_sum(mut happiness: Vec<i32>, k: i32) -> i64 {
    happiness.sort_unstable_by(|a, b| b.cmp(a));
    let mut sum = 0i64;
    for (turn, &h) in happiness.iter().take(k as usize).enumerate() {
      let val = (h - turn as i32).max(0);
      sum += val as i64;
    }
    sum
  }
}