<p>Given an integer array <code>nums</code> and two integers <code>lower</code> and <code>upper</code>, return <em>the number of range sums that lie in</em> <code>[lower, upper]</code> <em>inclusive</em>.</p>

<p>Range sum <code>S(i, j)</code> is defined as the sum of the elements in <code>nums</code> between indices <code>i</code> and <code>j</code> inclusive, where <code>i &lt;= j</code>.</p>

<p>&nbsp;</p>
<p><strong class="example">Example 1:</strong></p>

<pre>
<strong>Input:</strong> nums = [-2,5,-1], lower = -2, upper = 2
<strong>Output:</strong> 3
<strong>Explanation:</strong> The three ranges are: [0,0], [2,2], and [0,2] and their respective sums are: -2, -1, 2.
</pre>

<p><strong class="example">Example 2:</strong></p>

<pre>
<strong>Input:</strong> nums = [0], lower = 0, upper = 0
<strong>Output:</strong> 1
</pre>

<p>&nbsp;</p>
<p><strong>Constraints:</strong></p>

<ul>
	<li><code>1 &lt;= nums.length &lt;= 10<sup>5</sup></code></li>
	<li><code>-2<sup>31</sup> &lt;= nums[i] &lt;= 2<sup>31</sup> - 1</code></li>
	<li><code>-10<sup>5</sup> &lt;= lower &lt;= upper &lt;= 10<sup>5</sup></code></li>
	<li>The answer is <strong>guaranteed</strong> to fit in a <strong>32-bit</strong> integer.</li>
</ul>

void merge(vector<long long>& arr,int start,int mid,int end,int &lower,int &upper,long long &count,long long &count1){
    int s1=mid-start+1;
    int s2=end-mid;
    vector<long long> l(s1,0);
    vector<long long> r(s2,0);
    for(int i=0;i<s1;i++){
        l[i]=arr[start+i];
    }
    for(int i=0;i<s2;i++){
        r[i]=arr[mid+1+i];
    }
    int i=0;
    int j=0;
    while(i<s1 && j<s2){
        if(r[j]-l[i] <= upper){
            count=count+s1-i;
            j++;
        }
        else{
            i++;
        }
    }
    i=0;
    j=0;
    while(i<s1 && j<s2){
        if(r[j]-l[i] < lower){
            count1=count1+s1-i;
            j++;
        }
        else{
            i++;
        }
    }
    i=0;
    j=0;
    int k=start;
    while(i<s1 && j<s2){
        if(l[i] <= r[j]){
            arr[k]=l[i];
            i++;
        }
        else{
            arr[k]=r[j];
            j++;
        }
        k++;
    }
    while(i<s1){
        arr[k]=l[i];
        i++;
        k++;
    }
    while(j<s2){
        arr[k]=r[j];
        j++;
        k++;
    }
}
void mergesort(vector<long long>& arr,int start,int end,int &lower,int &upper,long long &count,long long &count1){
    if(start >= end)return;
    int mid=(start+end)/2;
    mergesort(arr,start,mid,lower,upper,count,count1);
    mergesort(arr,mid+1,end,lower,upper,count,count1);
    merge(arr,start,mid,end,lower,upper,count,count1);
}
class Solution {
public:
    int countRangeSum(vector<int>& nums, int lower, int upper) {
        vector<long long> arr;
        int n=nums.size();
        arr.push_back(0);
        long long sum=0;
        for(int i=0;i<n;i++){
            sum=sum+nums[i];
            arr.push_back(sum);
        }
        long long count=0;
        long long count1=0;
        mergesort(arr,0,n,lower,upper,count,count1);
        return count-count1;

    }
};
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