内卷地狱
CareerInterview prepLeetCode Solutions

1664. Ways to Make a Fair Array — Daily Problem

Edit Me

1664. Ways to Make a Fair Array

Approach

When reading the problem, I immediately knew we shouldn't actually delete elements one by one — that would time out. So I tried a "pure Python" approach using slices to process all the data, but it still timed out.

Then I checked the official solution, which uses dynamic programming. The key insight is:

In general, suppose we delete element at index i. Obviously, elements before index i remain unchanged. Elements originally at index j where j > i shift to index j − 1. Therefore, elements after index i that were at even indices become odd, and vice versa.

Code

class Solution:
    def waysToMakeFair(self, nums: List[int]) -> int:
        flag = 0
        for i in range(len(nums)):
            temp_nums = nums[:i] + nums[i+1:]
            if sum(temp_nums[::2])==sum(temp_nums[1::2]):
                flag += 1
        return flag
class Solution:
    def waysToMakeFair(self, nums: List[int]) -> int:
        res = odd1 = even1 = odd2 = even2 = 0
        for i, num in enumerate(nums):
            if i & 1:
                odd2 += num
            else:
                even2 += num
        for i, num in enumerate(nums):
            if i & 1:
                odd2 -= num
            else:
                even2 -= num
            if odd1 + even2 == odd2 + even1:
                res += 1
            if i & 1:
                odd1 += num
            else:
                even1 += num
        return res

贡献者

这篇文章有帮助吗？

最近更新

Involution Hell© 2026 byCommunityunderCC BY-NC-SA 4.0CCBYNCSA

1653. Minimum Deletions to Make String Balanced

LeetCode 1653. Minimum Deletions to Make String Balanced — DP and stack-free counting with two passes, tracking 'a' and 'b' counts to minimize deletions for CS learners.

1664. Number of schemes to generate balance numbers One question daily

LeetCode 1664. 生成平衡数组的方案数 题解 — 使用动态规划与奇偶性分析，核心技巧是预处理前缀奇偶和与后缀奇偶和，在枚举删除每个元素时 O(1) 判断剩余数组奇偶下标和是否相等。适合准备算法面试、刷 LeetCode 中等题的求职者和 CS 学生。

On this page

ApproachCode