How hard is LeetCode 1099. Two Sum Less Than K?

LeetCode 1099. Two Sum Less Than K is rated Easy on LeetCode.

What is the time complexity of LeetCode 1099. Two Sum Less Than K?

The Python solution on this page runs in O(n \times \log n).

What is the space complexity of LeetCode 1099. Two Sum Less Than K?

The Python solution on this page uses O(\log n) auxiliary space.

What topics does LeetCode 1099. Two Sum Less Than K cover?

LeetCode 1099. Two Sum Less Than K is tagged Array, Two Pointers, Binary Search and Sorting on LeetCode.

Is LeetCode 1099. Two Sum Less Than K a premium problem?

Yes. LeetCode 1099. Two Sum Less Than K is a LeetCode Premium problem, so the full statement and test cases require a paid LeetCode subscription.

Two Sum Less Than K — LeetCode 1099 Python Solution

EasyLeetCode PremiumArrayTwo PointersBinary SearchSorting

Problem: #1099
Pattern: Two Pointers
Reading time: 2 min
Source: leetcode.com

The problem

Given an array nums of integers and integer k, return the maximum sum such that there exists i < j with nums[i] + nums[j] = sum and sum < k. If no i, j exist satisfying this equation, return -1.

Example

Input: nums = [34,23,1,24,75,33,54,8], k = 60
Output: 58
Explanation: We can use 34 and 24 to sum 58 which is less than 60.

Python solution

Python

class Solution:
    def twoSumLessThanK(self, nums: List[int], k: int) -> int:
        nums.sort()
        ans = -1
        for i, x in enumerate(nums):
            j = bisect_left(nums, k - x, lo=i + 1) - 1
            if i < j:
                ans = max(ans, x + nums[j])
        return ans

Complexity

Measure	Complexity
Time	O(n \times \log n)
Space	O(\log n) auxiliary

Pattern: Two Pointers

Use the order already in the input to discard half the search space at every step. LeetCode 1099. Two Sum Less Than K is filed here on both counts: the reference solution below belongs to the algorithm family this hub collects, and LeetCode tags it Two Pointers.

The two pointers guide has the Python template for the pattern and the 201 LeetCode problems that use it.

Frequently asked questions

How hard is LeetCode 1099. Two Sum Less Than K?: LeetCode 1099. Two Sum Less Than K is rated Easy on LeetCode.
What is the time complexity of LeetCode 1099. Two Sum Less Than K?: The Python solution on this page runs in O(n \times \log n).
What is the space complexity of LeetCode 1099. Two Sum Less Than K?: The Python solution on this page uses O(\log n) auxiliary space.
What topics does LeetCode 1099. Two Sum Less Than K cover?: LeetCode 1099. Two Sum Less Than K is tagged Array, Two Pointers, Binary Search and Sorting on LeetCode.
Is LeetCode 1099. Two Sum Less Than K a premium problem?: Yes. LeetCode 1099. Two Sum Less Than K is a LeetCode Premium problem, so the full statement and test cases require a paid LeetCode subscription.