<p>You are given an integer array&nbsp;<code>nums</code>. You can choose <strong>exactly one</strong> index (<strong>0-indexed</strong>) and remove the element. Notice that the index of the elements may change after the removal.</p>

<p>For example, if <code>nums = [6,1,7,4,1]</code>:</p>

<ul>
	<li>Choosing to remove index <code>1</code> results in <code>nums = [6,7,4,1]</code>.</li>
	<li>Choosing to remove index <code>2</code> results in <code>nums = [6,1,4,1]</code>.</li>
	<li>Choosing to remove index <code>4</code> results in <code>nums = [6,1,7,4]</code>.</li>
</ul>

<p>An array is <strong>fair</strong> if the sum of the odd-indexed values equals the sum of the even-indexed values.</p>

<p>Return the <em><strong>number</strong> of indices that you could choose such that after the removal, </em><code>nums</code><em> </em><em>is <strong>fair</strong>. </em></p>

<p>&nbsp;</p>
<p><strong class="example">Example 1:</strong></p>

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

<p><strong class="example">Example 2:</strong></p>

<pre>
<strong>Input:</strong> nums = [1,1,1]
<strong>Output:</strong> 3
<strong>Explanation:</strong>&nbsp;You can remove any index and the remaining array is fair.
</pre>

<p><strong class="example">Example 3:</strong></p>

<pre>
<strong>Input:</strong> nums = [1,2,3]
<strong>Output:</strong> 0
<strong>Explanation:</strong>&nbsp;You cannot make a fair array after removing any index.
</pre>

<p>&nbsp;</p>
<p><strong>Constraints:</strong></p>

<ul>
	<li><code>1 &lt;= nums.length &lt;= 10<sup>5</sup></code></li>
	<li><code>1 &lt;= nums[i] &lt;= 10<sup>4</sup></code></li>
</ul>

class Solution:
    def waysToMakeFair(self, nums: List[int]) -> int:
        
        # l_even, l_odd 分别表示以nums[0]作为起点，所有偶数/奇数indices的和
        l_even = [-1] * len(nums)
        l_odd = [-1] * len(nums)
        
        for i in range(len(nums)):
            if i == 0:
                l_even[i], l_odd[i] = nums[0], 0
                continue
                
            if i % 2 == 0:
                l_even[i] = l_even[i-1] + nums[i]
                l_odd[i] = l_odd[i-1] 
            else:
                l_even[i] = l_even[i-1]
                l_odd[i] = l_odd[i-1] + nums[i]
                
                
        # cur_even, cur_odd表示移nums[current]为起点，所有偶数/奇数indices的和
        cur_even = [-1] * len(nums)
        cur_odd = [-1] * len(nums)
        
        for i in range(len(nums)-1, -1, -1):
            if i == len(nums)-1:
                cur_even[i] = nums[i]
                cur_odd[i] = 0
                continue
                
            cur_even[i] = nums[i] + cur_odd[i+1]
            cur_odd[i] = cur_even[i+1]
                
                
        res = 0
        for i in range(len(nums)):
            e, o = 0, 0
            
            if i > 0:
                e += l_even[i-1]
                o += l_odd[i-1]
                
            if i < len(nums)-1:
                if i % 2 == 0:
                    o += cur_odd[i+1]
                    e += cur_even[i+1]
                else:
                    o += cur_even[i+1]
                    e += cur_odd[i+1]
                    
            if e == o:
                res += 1
                
        return res
                    
                    
                    
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