<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 e){
    int mid=(s+e)/2;

    int len1=mid-s+1;
    int len2=e-mid;

    int *first=new int[len1];
    int *second = new int[len2];

    //copy values

    int k=s;
    for(int i=0;i<len1;i++){
        first[i]=arr[k++];
    }

    k=mid+1;
    for(int i=0;i<len2;i++){
        second[i]=arr[k++];
    }

    //merge 2 sorted array
    //k=mainarrayindex

    int index1 = 0;
    int index2 = 0;
    k=s;
    while(index1 < len1 && index2 < len2){
        if(first[index1] < second[index2]){
            arr[k++]=first[index1++];
        }
        else{
            arr[k++]=second[index2++];
        }
    }

    while(index1<len1){
        arr[k++]=first[index1++];
    }

    while(index2<len2){
        arr[k++]=second[index2++];
    }
    delete []first;
    delete []second;
}

void mergesort(vector<int>& arr,int s,int e){
    //base case
    if(s>=e){
        return;
    }

    int mid=(s+e)/2;

    //left part sort karna hai 
    mergesort(arr,s,mid);

    //right part sort karna hai
    mergesort(arr,mid+1,e);

    //mergr karna hai
    merge(arr,s,e);
}

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