无左右索引跟踪的快速排序

我需要实现快速排序算法,对动态分配内存的数组进行排序。我试着写一些代码:

#include <stdio.h>
// function to swap elements
void swap(int *a, int *b) {
  int t = *a;
  *a = *b;
  *b = t;
}
// function to find the partition position
int partition(int array[], int low, int high) {
  // select the rightmost element as pivot
  int pivot = array[high];
  // pointer for greater element
  int i = (low - 1);
  // traverse each element of the array
  // compare them with the pivot
  for (int j = low; j < high; j++) {
    if (array[j] <= pivot) {
      // if element smaller than pivot is found
      // swap it with the greater element pointed by i
      i++;
      // swap element at i with element at j
      swap(&array[i], &array[j]);
    }
  }
  // swap the pivot element with the greater element at i
  swap(&array[i + 1], &array[high]);
  // return the partition point
  return (i + 1);
}
void quickSort(int array[], int low, int high) {
  if (low < high) {
    // find the pivot element such that
    // elements smaller than pivot are on left of pivot
    // elements greater than pivot are on right of pivot
    int pi = partition(array, low, high);
    // recursive call on the left of pivot
    quickSort(array, low, pi - 1);
    // recursive call on the right of pivot
    quickSort(array, pi + 1, high);
  }
}
// function to print array elements
void printArray(int array[], int size) {
  for (int i = 0; i < size; ++i) {
    printf("%d  ", array[i]);
  }
  printf("\n");
}
// main function
int main() {
  size_t n = 8;
  int *x = malloc( n * sizeof( int ) );
  memcpy( x, ( int[] ){8, 7, 2, 1, 0, 9, 6,0}, n * sizeof( int ) ); // need <string.h>
  printf("Unsorted Array\n");
  printArray(x, n);
  // perform quick-sort on data
  quickSort(x, n);
  printf("Sorted array in ascending order: \n");
  printArray(x, n);
  free(x);
}

问题是,给出的指令是将函数编写为 quickSort(int* x, int n) 结构但我当时非常困惑,递归函数是如何知道左右索引的?

另一个问题是,测试我的程序的最佳方法是什么?比如如何高效地创建测试用例。我是一名中级python开发人员,在使用C编程时面临很多问题。