README.md

373. Find K Pairs with Smallest Sums

You are given two integer arrays nums1 and nums2 sorted in non-decreasing order and an integer k.

Define a pair (u, v) which consists of one element from the first array and one element from the second array.

Return the k pairs (u1, v1), (u2, v2), ..., (uk, vk) with the smallest sums.

Example 1:

Input: nums1 = [1,7,11], nums2 = [2,4,6], k = 3
Output: [[1,2],[1,4],[1,6]]
Explanation: The first 3 pairs are returned from the sequence: [1,2],[1,4],[1,6],[7,2],[7,4],[11,2],[7,6],[11,4],[11,6]

Example 2:

Input: nums1 = [1,1,2], nums2 = [1,2,3], k = 2
Output: [[1,1],[1,1]]
Explanation: The first 2 pairs are returned from the sequence: [1,1],[1,1],[1,2],[2,1],[1,2],[2,2],[1,3],[1,3],[2,3]

Constraints:

• 1 <= nums1.length, nums2.length <= 105
• -109 <= nums1[i], nums2[i] <= 109
• nums1 and nums2 both are sorted in non-decreasing order.
• 1 <= k <= 104
• k <= nums1.length * nums2.length

Solutions (Rust)

1. Solution

use std::cmp::Reverse;
use std::collections::BinaryHeap;

impl Solution {
    pub fn k_smallest_pairs(nums1: Vec<i32>, nums2: Vec<i32>, k: i32) -> Vec<Vec<i32>> {
        let mut heap = (0..nums1.len().min(k as usize))
            .map(|i| (Reverse(nums1[i] + nums2[0]), i, 0))
            .collect::<BinaryHeap<_>>();
        let mut ret = vec![];

        for _ in 0..k {
            let (_, i, j) = heap.pop().unwrap();

            if j + 1 < nums2.len() {
                heap.push((Reverse(nums1[i] + nums2[j + 1]), i, j + 1));
            }
            ret.push(vec![nums1[i], nums2[j]]);
        }

        ret
    }
}