编辑代码

#include <stdio.h>


int mergeAndCount(int arr[], int left[], int leftSize, int right[], int rightSize) {
    int i = 0, j = 0, k = 0;
    int count = 0;

    while (i < leftSize && j < rightSize) {
        if (left[i] <= right[j]) {
            arr[k++] = left[i++];
        } else {
            arr[k++] = right[j++];
            count += leftSize - i;
        }
    }

    while (i < leftSize) {
        arr[k++] = left[i++];
    }

    while (j < rightSize) {
        arr[k++] = right[j++];
    }

    return count;
}


int mergeSortAndCount(int arr[], int size) {
    if (size <= 1) {
        return 0;
    }

    int mid = size / 2;
    int left[mid];
    int right[size - mid];

    
    for (int i = 0; i < mid; i++) {
        left[i] = arr[i];
    }

    for (int i = mid; i < size; i++) {
        right[i - mid] = arr[i];
    }


    int count = mergeSortAndCount(left, mid) + mergeSortAndCount(right, size - mid);

  
    count += mergeAndCount(arr, left, mid, right, size - mid);

    return count;
}

int main() {
    int arr[] = { 5, 3, 8, 2, 4};
    int size = sizeof(arr) / sizeof(arr[0]);
    printf("原数组: ");
    for (int i = 0; i < size; i++) {
        printf("%d ", arr[i]);
    }
    printf("\n");
    int count = mergeSortAndCount(arr, size);
    printf("逆序对个数: %d\n", count);

}