- Difficulty: Medium
- Tags: LeetCode, Medium, Greedy, Array, Sorting, leetcode-2098, O(n) on average, O(1), 🔒, Quick Select
Problem
You are given an integer array nums and an integer k. Find the largest even sum of any subsequence of nums that has a length of k.
Return this sum, or -1 if such a sum does not exist.
A subsequence is an array that can be derived from another array by deleting some or no elements without changing the order of the remaining elements.
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Example 1:
Input: nums = [4,1,5,3,1], k = 3 Output: 12 Explanation: The subsequence with the largest possible even sum is [4,5,3]. It has a sum of 4 + 5 + 3 = 12.
Example 2:
Input: nums = [4,6,2], k = 3 Output: 12 Explanation: The subsequence with the largest possible even sum is [4,6,2]. It has a sum of 4 + 6 + 2 = 12.
Example 3:
Input: nums = [1,3,5], k = 1 Output: -1 Explanation: No subsequence of nums with length 1 has an even sum.
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Constraints:
1 <= nums.length <= 1050 <= nums[i] <= 1051 <= k <= nums.length