Maximize Sum Of Array After K Negations — LeetCode 1005 Python Solution

The problem

Given an integer array nums and an integer k, modify the array in the following way: choose an index i and replace nums[i] with -nums[i]. You should apply this process exactly k times.

Example

Input

nums = [4,2,3], k = 1

Output

5

Explanation

Choose index 1 and nums becomes [4,-2,3].

Python solution

class Solution:
    def largestSumAfterKNegations(self, nums: List[int], k: int) -> int:
        cnt = Counter(nums)
        for x in range(-100, 0):
            if cnt[x]:
                m = min(cnt[x], k)
                cnt[x] -= m
                cnt[-x] += m
                k -= m
                if k == 0:
                    break
        if k & 1 and cnt[0] == 0:
            for x in range(1, 101):
                if cnt[x]:
                    cnt[x] -= 1
                    cnt[-x] += 1
                    break
        return sum(x * v for x, v in cnt.items())

Complexity

Pattern: Greedy

Take the locally best option every time — when you can prove that never costs you later. LeetCode 1005. Maximize Sum Of Array After K Negations is filed here on both counts: the reference solution below belongs to the algorithm family this hub collects, and LeetCode tags it Greedy.

The greedy guide has the Python template for the pattern and the 346 LeetCode problems that use it.

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