<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 {
public:
    int waysToMakeFair(vector<int>& nums) {
        
        int n=nums.size();
        if(n==1)
            return 1;
        int sume=0,sumo=0;
        vector<int>prefe,prefo;
        for(int i=0;i<n;i++)
        {

            if(i%2==0)
            {
                sume+=nums[i];
                prefe.push_back(sume);
            }
            else
            {
                sumo+=nums[i];
                 prefo.push_back(sumo);
            }
        }

        int ways=0;
        if(sume-nums[0]==sumo)
            ways++;
       
        for(int i=1;i<n;i++)
        {
            int prevE=0,prevO=0;
            
            if(i%2==1)
            {    
                prevE=prefe[(i-1)/2];
                if(i/2-1>=0)
                    prevO=prefo[i/2-1];
            }

            else
            {
                prevE=prefe[i/2-1];
                if(i/2-1>=0)
                    prevO=prefo[i/2-1];
            }

            int lastOddInd=n/2-1;
            int lastEvenInd=n%2==0?(n)/2-1:(n-1)/2;

            if(i%2==1)
            {

                int se=prevE + prefo[lastOddInd]- prevO -nums[i];

                    int so=prevO + prefe[lastEvenInd]- prevE;
                
                if(se==so)
                    ways++;
               //  cout<<i<<" "<<se<<" "<<so<<endl;
            }

            else
            {
                 int se=prevE + prefo[lastOddInd]- prevO;

                    int so=prevO + prefe[lastEvenInd]- prevE  -nums[i];
                
                if(se==so)
                    ways++;
               //  cout<<i<<" "<<se<<" "<<so<<endl;
            }

          
        }
        return ways;
    }
};
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