<p>Given an array of integers <code>nums</code>, half of the integers in <code>nums</code> are <strong>odd</strong>, and the other half are <strong>even</strong>.</p>

<p>Sort the array so that whenever <code>nums[i]</code> is odd, <code>i</code> is <strong>odd</strong>, and whenever <code>nums[i]</code> is even, <code>i</code> is <strong>even</strong>.</p>

<p>Return <em>any answer array that satisfies this condition</em>.</p>

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

<pre>
<strong>Input:</strong> nums = [4,2,5,7]
<strong>Output:</strong> [4,5,2,7]
<strong>Explanation:</strong> [4,7,2,5], [2,5,4,7], [2,7,4,5] would also have been accepted.
</pre>

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

<pre>
<strong>Input:</strong> nums = [2,3]
<strong>Output:</strong> [2,3]
</pre>

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

<ul>
	<li><code>2 &lt;= nums.length &lt;= 2 * 10<sup>4</sup></code></li>
	<li><code>nums.length</code> is even.</li>
	<li>Half of the integers in <code>nums</code> are even.</li>
	<li><code>0 &lt;= nums[i] &lt;= 1000</code></li>
</ul>

<p>&nbsp;</p>
<p><strong>Follow Up:</strong> Could you solve it in-place?</p>

class Solution {
public:
    vector<int> sortArrayByParityII(vector<int>& nums) {
        stack<int*> odds;
        stack<int*> evens;
        
        for (int i = 0; i < nums.size(); i++) {
            auto n = nums[i];
            if (i%2 != n%2) {
                switch (n%2) {
                    case 0: 
                        if (odds.empty()) evens.push(&nums[i]);
                        else {
                            nums[i] = *odds.top();
                            *odds.top() = n;
                            odds.pop();
                    }
                    break;
                    case 1:
                        if (evens.empty()) odds.push(&nums[i]);
                        else {
                            nums[i] = *evens.top();
                            *evens.top() = n;
                            evens.pop();
                        }
                    break;
                }
            }
        }
        return nums;
    }
};
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