<p>Given an array of integers <code>nums</code>, sort the array in ascending order and return it.</p>

<p>You must solve the problem <strong>without using any built-in</strong> functions in <code>O(nlog(n))</code> time complexity and with the smallest space complexity possible.</p>

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

<pre>
<strong>Input:</strong> nums = [5,2,3,1]
<strong>Output:</strong> [1,2,3,5]
<strong>Explanation:</strong> After sorting the array, the positions of some numbers are not changed (for example, 2 and 3), while the positions of other numbers are changed (for example, 1 and 5).
</pre>

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

<pre>
<strong>Input:</strong> nums = [5,1,1,2,0,0]
<strong>Output:</strong> [0,0,1,1,2,5]
<strong>Explanation:</strong> Note that the values of nums are not necessairly unique.
</pre>

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

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

class Solution {
public:
    void merge(vector<int>& nums, int left, int mid, int right) {
        vector<int> temp{};
        for(int i=left;i<=mid;++i) {
            temp.push_back(nums[i]);
        }
        for(int i=mid+1;i<=right;++i) {
            temp.push_back(nums[i]);
        }
        int startIndex = left, lTotal = mid - left +1, rTotal = right - left + 1, lIndex = 0, rIndex = lTotal;
        while(lIndex != lTotal && rIndex != rTotal) {
            if(temp[lIndex]<= temp[rIndex]) {
                nums[startIndex] = temp[lIndex];
                ++lIndex;
            }else{
                nums[startIndex] = temp[rIndex];
                ++rIndex;
            }
            ++startIndex;
        }
        for(int i=lIndex;lIndex!=lTotal;++lIndex) {
            nums[startIndex] = temp[lIndex];
            ++startIndex;
        }

        for(int i=rIndex;rIndex!=rTotal;++rIndex) {
            nums[startIndex] = temp[rIndex];
            ++startIndex;
        }
    }
    void mergeSort(vector<int>& nums, int left, int right){
        if(left >= right) {
            return;
        }
        int mid = left + (right-left)/2;
        mergeSort(nums, left, mid);
        mergeSort(nums, mid+1, right);
        merge(nums, left, mid, right);
    }
    vector<int> sortArray(vector<int>& nums) {
        mergeSort(nums, 0, nums.size()-1);
        return nums;
    }
};
254611