<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> helper1(int s, int e, vector<int> &nums){
        //base case
        // cout<<s<<" "<<e<<endl;
        if(e<=s){
            return {nums[s]};
        }

        int mid = (e+s)/2;
        vector<int> leftHalf = helper1(s, mid, nums);
        vector<int> rightHalf = helper1(mid+1, e, nums);

        //sort the sorted arrays
        int m = leftHalf.size();
        int n = rightHalf.size();
        vector<int> ans(m+n);
        int i=0,j=0;
        int k=0;
        while(i < m && j < n){
            if(leftHalf[i]<rightHalf[j]){
                ans[k++]=leftHalf[i++];
            }
            else{
                ans[k++]=rightHalf[j++];
            }
        }
        while(i<m){
            ans[k++]=leftHalf[i++];
        }
        while(j<n){
            ans[k++]=rightHalf[j++];
        }

        return ans;

    }
    vector<int> sortArray(vector<int>& nums) {
        int n = nums.size();
        vector<int> ans(n);
        return helper1(0, n-1, nums);
    }
};
188633