编辑代码

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

void merge(int arr[], int left, int mid, int right) {
    int i, j, k;
    int n1 = mid - left + 1;
    int n2 = right - mid;

    int L[n1], R[n2];

    for (i = 0; i < n1; i++)
        L[i] = arr[left + i];
    for (j = 0; j < n2; j++)
        R[j] = arr[mid + 1 + j];

    i = 0;
    j = 0;
    k = left;

    while (i < n1 && j < n2) {
        if (L[i] <= R[j]) {
            arr[k] = L[i];
            i++;
        }
        else {
            arr[k] = R[j];
            j++;
        }
        k++;
    }

    while (i < n1) {
        arr[k] = L[i];
        i++;
        k++;
    }

    while (j < n2) {
        arr[k] = R[j];
        j++;
        k++;
    }
}

void mergeSort(int arr[], int left, int right) {
    if (left < right) {
        int mid = left + (right - left) / 2;
        mergeSort(arr, left, mid);
        mergeSort(arr, mid + 1, right);
        merge(arr, left, mid, right);
    }
}
int main() {
    // 测试用例1:正常情况
    int arr1[5] = { 5, 4, 3, 2, 1 };
    int n1 = sizeof(arr1) / sizeof(arr1[0]);
    printf("原数组1:");
    for (int i = 0; i < n1; i++)
        printf("%d ", arr1[i]);
    printf("\n");
    mergeSort(arr1, 0, n1 - 1);
    printf("排序后1:");
    for (int i = 0; i < n1; i++)
        printf("%d ", arr1[i]);
    printf("\n\n");
    // 测试用例2:异常情况
    int arr2[5] = { 5, 4, 3 };
    int n2 = sizeof(arr2) / sizeof(arr2[0]);
    printf("原数组2:");
    for (int i = 0; i < n2; i++)
        printf("%d ", arr2[i]);
    printf("\n");
    mergeSort(arr2, 0, n2 - 1);
    printf("排序后2:");
    for (int i = 0; i < n2; i++)
        printf("%d ", arr2[i]);
    printf("\n\n");
    // 测试用例3:全为1
    int arr3[5] = { 1, 1, 1, 1, 1 };
    int n3 = sizeof(arr3) / sizeof(arr3[0]);
    printf("原数组3:");
    for (int i = 0; i < n3; i++)
        printf("%d ", arr3[i]);
    printf("\n");
    mergeSort(arr3, 0, n3 - 1);
    printf("排序后3:");
    for (int i = 0; i < n3; i++)
        printf("%d ", arr3[i]);
    printf("\n\n");
    return 0;
}