<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 {
    void mergeSort(vector<int>& nums, int start, int end){
        int mid;
        if(start == end)
            return ;
        mid = start + (end-start)/2;
        mergeSort(nums, start, mid);
        mergeSort(nums, mid+1, end);
        merge(nums, start, mid, end);
    }

    void merge(vector<int>&nums, int start, int mid, int end){
        vector<int> temp(end-start+1);
        int left = start, right = mid+1, index = 0;
        while(left<=mid && right<=end){
            if(nums[left]<=nums[right]){
                temp[index] = nums[left];
                index++, left++;
            }
            else{
                temp[index] = nums[right];
                index++, right++;
            }
        }

        while(left<=mid){
            temp[index] = nums[left];
                index++, left++;
        }
        while(right<=end){
            temp[index] = nums[right];
            index++, right++;
        }

        index = 0;
        while(start<=end){
            nums[start] = temp[index];
            start++, index++;
        }
    }
public:
    vector<int> sortArray(vector<int>& nums) {
        int start = 0, end = nums.size()-1;
        mergeSort(nums, start, end);
        return nums;
    }
};
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