<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>& arr,int s,int l){
        int mid=s+(l-s)/2;

        if(arr[mid]<arr[mid+1]){
            return;
        }
        vector<int> left;
        vector<int> right;

        for(int i=s;i<=mid;i++){
            left.push_back(arr[i]);
        }

        for(int i=mid+1;i<=l;i++){
            right.push_back(arr[i]);
        }

        int ptr1=0;
        int ptr2=0;

        int lefts=left.size();
        int rights=right.size();

        while(ptr1<lefts && ptr2<rights){
            
            if(left[ptr1]<=right[ptr2]){
                arr[s++]=left[ptr1++];    
            }
            else{
                arr[s++]=right[ptr2++]; 
            }

        }
        while(ptr1<lefts){
            arr[s++]=left[ptr1++];
        }

        while(ptr2<rights){
            arr[s++]=right[ptr2++];
        }

    }
    void mergesort(vector<int>& arr,int s,int l){
        if(s>=l){
            return;
        }
        int mid=s+(l-s)/2;

        mergesort(arr,s,mid);
        mergesort(arr,mid+1,l);

        merge(arr,s,l);

    }
    vector<int> sortArray(vector<int>& arr) {
        mergesort(arr,0,arr.size()-1);
        return arr;
    }
};
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