CSE2012 PP1 Q2

/*
Counting inversions
Inversion Count for an array indicates – how far (or close) the array is from being sorted. If array
is already sorted then inversion count is 0. If array is sorted in reverse order that inversion count
is the maximum. Formally speaking, two elements a[i] and a[j] form an inversion if a[i] > a[j]
and i < j.
Example: Input: arr[] = {8, 4, 2, 1}
Output: 6. The six inversions: (8,4), (4,2), (8,2), (8,1), (4,1), (2,1).
Input: arr[] = {3, 1, 2}
Output: 2. The two inversions: (3,1), (3,2).
*/

#include <stdio.h>
#include <stdlib.h>

void solve(){
    unsigned int size;
    int *arr;
    int i, j;
    // Input
    printf("Enter size of array: ");
    scanf("%u", &size);
    arr = (int *)malloc(sizeof(int)*size);

    printf("\nInput values: ");
    for(i = 0; i < size; i++){
        scanf("%d", &arr[i]);
    }

    //solving
    unsigned int inversions = 0;

    for (i = 0; i < size-1; i++){
        for(j = i+1; j < size; j++){
            if (arr[i] > arr[j]){
                inversions++;
            }
        }
    }

    printf("\nThe inversion count is %d\n", inversions);
}

int main(){
    solve();
    return 0;
}