Search⌘ K
AI Features
Home
Courses
Grokking the Coding Interview Patterns

Find K Pairs with Smallest Sums

Understand how to find the k pairs with the smallest sums from two sorted arrays by applying the k-way merge algorithm. This lesson guides you through the problem constraints and approaches to efficiently handle sorted data, helping you solve similar coding interview challenges.

We'll cover the following...

Statement

You are given two integer arrays, list1 and list2, sorted in non-decreasing order, and an integer, k.

A pair (u, v)(u, \space v) is defined as one element uu chosen from list1 and one element vv chosen from list2.

Your task is to return the k pairs (u1, v1),(u2, v2),...,(uk, vk)(u1, \space v1), (u2, \space v2), ..., (uk, \space vk) whose sums u1+v1,u2+v2,...,uk+vku1 + v1, u2 + v2, ..., uk + vk are the smallest among all possible such pairs.

Note: If multiple pairs have the same sum, any order among them is acceptable.

Constraints:

  • 11 ≤\leq list1.length, list2.length ≤\leq 500500

  • −104-10^4 ≤\leq list1[i], list2[i] ≤\leq 10410^4

  • 11 ≤\leq kk ≤\leq 10310^3

  • Input lists should be sorted in ascending order.

  • If the value of kk exceeds the total number of valid pairs that may be formed, return all the pairs.

Examples

Understand the problem

Let’s take a moment to make sure you’ve correctly understood the problem. The quiz below helps you check if you’re solving the correct problem:

Find K Pairs with Smallest Sums

1.

What is the output if the following lists and value of k is given as input?

list1 = [1, 11, 20, 35, 300]

list2 = [1, 2, 300]

k = 5

A.

pairs = [[1, 1], [1, 2], [1, 300], [11, 1], [11, 2]]

B.

pairs = [[1, 1], [1, 2], [11, 1], [11, 2], [11, 300]]

C.

pairs = [[1, 1], [1, 2], [11, 1], [11, 2], [20, 2]]

D.

pairs = [[1, 1], [1, 2], [11, 1], [11, 2], [20, 1]]

1 / 3

Figure it out!

We have a game for you to play. Rearrange the logical building blocks to develop a clearer understanding of how to solve this problem.

Sequence - Vertical
Drag and drop the cards to rearrange them in the correct sequence.
1
2
3
4
5

Try it yourself

Implement your solution in the following coding playground:

Java
usercode > FindKPairs.java
import java.util.*;
class FindKPairs {
    public static List<List<Integer>> kSmallestPairs(int[] list1, int[] list2, int target) {
        // Replace this placeholder return statement with your code
        return new ArrayList<>();
    }
}
Find K Pairs with Smallest Sums