如何打印合并排序的执行时间

Question

这里的示例程序输出

我这里有一个程序，允许用户输入随机生成的数字的N。现在，我在打印它时遇到了问题。它打印的不仅仅是执行时间。

void merge_sort(int i, int j, int a[], int aux[]) {

    start = clock();
    if (j <= i) {
      // if the subsection is empty or a single element
      return;
    }
    int mid = (i + j) / 2;

    // left sub-array is a[i .. mid]
    // right sub-array is a[mid + 1 .. j]

    merge_sort(i, mid, a, aux);         // sort the left sub-array recursively
    merge_sort(mid + 1, j, a, aux);     // sort the right sub-array recursively

    int pointer_left = i;               // pointer_left points to the beginning of the left sub-array
    int pointer_right = mid + 1;        // pointer_right points to the beginning of the right sub-array
    int k;                              // k is the loop counter

    // we loop from i to j to fill each element of the final merged array
    for (k = i; k <= j; k++) {
        if (pointer_left == mid + 1) {                      // left pointer has reached the limit
            aux[k] = a[pointer_right];
            pointer_right++;
        } else if (pointer_right == j + 1) {                // right pointer has reached the limit
            aux[k] = a[pointer_left];
            pointer_left++;
        } else if (a[pointer_left] < a[pointer_right]) {     // pointer left points to smaller element
            aux[k] = a[pointer_left];
            pointer_left++;
        } else {        // pointer right points to smaller element
            aux[k] = a[pointer_right];
            pointer_right++;
        }
    }
    // copy the elements from aux[] to a[]
    for (k = i; k <= j; k++) {
        a[k] = aux[k];
    }
    end = clock();
    cpu_time_used = ((double) (end - start)) / CLOCKS_PER_SEC;
    printf("TIME: %f\n", cpu_time_used);
}

// main method
int main(){

    int size, i;
    printf("Enter N: ");
    scanf("%d", &size);
    int array[size];
    int aux[size];
    if(size <= 0)
    {
        printf("\n Error!\n");
    }

    for (i = 0; i < size; i++)
    {
        array[i] = rand() % MAXRANGE;

    }

    printf("\nMerge Sorted: ");
    merge_sort(0, size - 1, array, aux);
    printArray(array, size);

    return 0;
}

我不知道在哪里放置clock()调用或计算执行时间。是印刷后的吗？

Answer 1

以下是一些指导方针：

用于获得执行时间：

include <time.h>
int main(){
    struct timeval stop,start;
    int arr[10000];
    gettimeofday(&start,NULL);
    mergeSort(arr, 100);
    gettimeofday(&stop,NULL);
    printf("Time taken for Quick sort is: %ld microseconds\n", 
        (stop.tv_sec-start.tv_sec)*1000000+stop.tv_usec-start.tv_usec);
}