Merge pull request tarunsinghofficial#1795 from MdAnsar7/main

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C Program/inversion_count.cpp

@@ -0,0 +1,78 @@
+#include <bits/stdc++.h>
+using namespace std;
+int merge(int arr[], int low, int mid, int high)
+{
+    int i = low, j = mid + 1, k = low;
+    int b[high];
+    int count=0;
+    while (i <= mid && j <= high)
+    {
+        if (arr[i] <= arr[j])
+        {
+            b[k] = arr[i];
+            i++;
+            k++;
+        }
+        else
+        {
+            b[k] = arr[j];
+            j++;
+            k++;
+            count+=mid+1-i;
+        }
+    }
+    if (i > mid)
+    {
+        while (j<=high)
+        {
+            b[k]=arr[j];
+            j++;
+            k++;
+        }
+
+    }
+    else{
+        while (i<=mid)
+        {
+            b[k]=arr[i];
+            i++;
+            k++;
+        }
+
+    }
+    for(k=low;k<=high;k++)
+    arr[k]=b[k];
+
+    return count;
+}
+int mergesort(int arr[], int low, int high)
+{
+    int mid;
+    int count = 0;
+    if (high > low)
+    {
+        mid = (high + low) / 2;
+        count += mergesort(arr, low, mid);
+        count += mergesort(arr, mid + 1, high);
+        count += merge(arr, low, mid, high);
+    }
+
+    return count;
+}
+int main()
+{
+
+    int n;
+    cout << "enter array length=";
+    cin >> n;
+    int arr[n];
+    cout << "\n enter array to be sorted=";
+    for (int i = 0; i < n; i++)
+    {
+        cin >> arr[i];
+    }
+
+    cout << mergesort(arr, 0, n);
+    cout << endl;
+return 0;
+}