【leetcode】1664. Ways to Make a Fair Array

题目如下：

You are given an integer array nums. You can choose exactly one index (0-indexed) and remove the element. Notice that the index of the elements may change after the removal.

For example, if nums = [6,1,7,4,1]:

• Choosing to remove index 1 results in nums = [6,7,4,1].
• Choosing to remove index 2 results in nums = [6,1,4,1].
• Choosing to remove index 4 results in nums = [6,1,7,4].

An array is fair if the sum of the odd-indexed values equals the sum of the even-indexed values.

Return the number of indices that you could choose such that after the removal, nums is fair.

 

Example 1:

Input: nums = [2,1,6,4]
Output: 1
Explanation:
Remove index 0: [1,6,4] -> Even sum: 1 + 4 = 5. Odd sum: 6. Not fair.
Remove index 1: [2,6,4] -> Even sum: 2 + 4 = 6. Odd sum: 6. Fair.
Remove index 2: [2,1,4] -> Even sum: 2 + 4 = 6. Odd sum: 1. Not fair.
Remove index 3: [2,1,6] -> Even sum: 2 + 6 = 8. Odd sum: 1. Not fair.
There is 1 index that you can remove to make nums fair.

Example 2:

Input: nums = [1,1,1]
Output: 3
Explanation: You can remove any index and the remaining array is fair.

Example 3:

Input: nums = [1,2,3]
Output: 0
Explanation: You cannot make a fair array after removing any index.

Constraints:

• 1 <= nums.length <= 105
• 1 <= nums[i] <= 104

解题思路：题目本身不难，而且nums.length 最大只有105，可以随便折腾。

代码如下：

class Solution(object):
    def waysToMakeFair(self, nums):
        """
        :type nums: List[int]
        :rtype: int
        """
        res = 0
        even = []
        odd = []
        even_amount = odd_amount = 0
        for i in range(len(nums)):
            if i % 2 == 0:
                even_amount += nums[i]
            else:
                odd_amount += nums[i]
            even.append(even_amount)
            odd.append(odd_amount)

        even_amount = odd_amount = 0
        for i in range(len(nums)):
            if even_amount + (odd[-1] - odd[i]) == odd_amount + (even[-1] - even[i]):
                res += 1
            if i % 2 == 0:
                even_amount += nums[i]
            else:
                odd_amount += nums[i]

        #print even
        #print odd

        return res