ARRAY INVERSION

• Problem Description

  
  Number of an inversion in array is the number of pair(a[i],a[j]) of elements such that i < j and a[i] > a[j]. For an example if we have a list of element 2 3 6 9 1 then number of inversion is 4 and the pairs are (2,1), (3,1), (6,1) and (9,1).
  Input:
  The first line is N, N is the size of array.
  The second line contains N input C[i].
  

• CODING ARENA::

• #include <stdio.h>

  int arrinv(int ar[], int a)

  {

    int i,j,c=0;

    for(i=0;i<a;i++)

    {

      for(j=i+1;j<a;j++)

      {

        if(ar[i]>ar[j])

          c++;

      }

    }

    return c;

  }

          

  int main()

  {

    int a,i;

    scanf("%d",&a);

    int arr[a];

    for(i=0;i<=a;i++)

    {

      scanf("%d",&arr[i]);

    }

    printf("%d",arrinv(arr,a));

  
  

  return 0;

  }

• Test Case 1

  
  Input (stdin)

  5
  
  2 3 6 9 1
  
  

  Expected Output

  4

• Test Case 2

  
  Input (stdin)

  5
  
  1 2 3 5 6
  
  

  Expected Output

  0