Max number of k sum pairs

Array Hash Table Two Pointers Sorting

56.9% acceptance

Feb 25, 2026

3540

122

You are given an integer array nums and an integer k. In one operation, you can pick two numbers from the array whose sum equals k and remove them. Return the maximum number of operations you can perform.

Solution

Rust

Time O(n log n)

Space O(1)

LeetCode

solution.rs

impl Solution {
  pub fn max_operations(mut nums: Vec<i32>, k: i32) -> i32 {
    nums.sort_unstable();
    let mut left = 0;
    let mut right = nums.len() - 1;
    let mut ops = 0;
    while left < right {
      let sum = nums[left] + nums[right];
      match sum.cmp(&k) {
        std::cmp::Ordering::Equal => {
          ops += 1;
          left += 1;
          right -= 1;
        }
        std::cmp::Ordering::Less => left += 1,
        std::cmp::Ordering::Greater => right -= 1,
      }
    }
    ops
  }
}