<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:
    vector<int>a;
    vector<int>b;
    vector<int>num;
    void mergeSort(int start, int end, int mid)
    {
        int j=0;
        for(int i=start;i<=mid;i++)
        {
            a[j]=num[i];
            j++;
        }
        int j1=0;
        for(int i=mid+1;i<=end;i++)
        {
            b[j1]=num[i];
            j1++;
        }
        int k=0;
        int k1=0;
        int l=start;
        while(k<j && k1<j1)
        {
            if(a[k]<=b[k1])
            {
                num[l]=a[k];
                k++;
            }
            else
            {
                num[l]=b[k1];
                k1++;
            }
            l++;
        }
        while(k<j)
        {
            num[l]=a[k];
            k++;
            l++;
        }
        while(k1<j1)
        {
            num[l]=b[k1];
            k1++;
            l++;
        }
    }
    void merge(int start,int end)
    {
        if(start==end)
        {
            return;
        }
        int mid=(start+end)/2;
        merge(start,mid);
        merge(mid+1,end);
        mergeSort(start,end,mid);
    }
    vector<int> sortArray(vector<int>& nums) {
        num.clear();
        a.clear();
        b.clear();
        num=nums;
        a=nums;
        b=nums;
        merge(0,nums.size()-1);
        return num;
    }
};
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