通過合並排序計算數組中的反轉

Question

數組的反轉計數指示–數組要排序的距離（或距離）。 如果數組已經排序，則反轉計數為0。如果數組以相反順序排序，則反轉計數為最大。

#include <iostream>
#include <cstdlib>
using namespace std;

int merge(int arr[],int temp[], int left, int mid, int right)
{
    int inv_count = 0;
    int i = left;
    int j = mid;
    int k = right;
    while((i <= mid-1) && (j <= right))
    {
        if(arr[i] <= arr[j])
        {
            temp[k++] = arr[i++];
        }
        else
        {
            temp[k++] = arr[j++];
            inv_count += (mid - i);
        }
    }
    while(i <= mid-1)
        temp[k++] = arr[i++];
    while(j <= right)
        temp[k++] = arr[j++];
    for(i = left; i <= right; i++)
        arr[i] = temp[i];
    return inv_count;
}

int _merge_sort(int arr[], int temp[], int left, int right)
{
    int mid, inv_count = 0;
    if(right > left)
    {
        mid = (right+left)/2;
        inv_count = _merge_sort(arr,temp,left,mid);
        inv_count += _merge_sort(arr,temp,mid+1,right);
        inv_count += merge(arr,temp,left,mid+1,right);
    }
    return inv_count;
 }

int merge_sort(int arr[], int array_size)
{
    int *temp = (int *)malloc(sizeof(int)*array_size);
    return (_merge_sort(arr,temp,0,array_size-1));
}

int main()
{
    int arr[]= {1, 25, 12, 56, 36, 3, 0, 10, 8, 7};
    for(int i = 0; i < 10; i++)
        cout<<arr[i]<<"\t";
    cout<<"\n";
    cout<<merge_sort(arr,10)<<"\n";
    for(int i = 0; i < 10; i++)
        cout<<arr[i]<<"\t";
    cout<<"\n";
    return 0;
}

給定數組的預期輸出為27，但我得到6。此外，原始數組數據已修改（未排序的值已更改）。

Answer 1

您需要在函數合並中用int k = left替換int k = right。 我認為此數組的預期輸出為27。此處討論了合並排序的各種實現，並在C ++中實現了合並排序。