排序-快排

快速排序：
快速排序操作如下，将数组a[r..p]分成两个子数组，a[p..q], a[q+1,r]，并且保证a[p..q]中的每一个值小于a[q+1,r]。然后再对每个子数组做相同的操作。

伪码：
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QuickSort

1.        If p < r then

a)        q Partition (A, p, r)

b)        Recursive call to Quick Sort (A, p, q)

c)         Recursive call to Quick Sort (A, q + r, r)

 

PARTITION (A, p, r)

1.        x ← A[p]

2.        i ← p-1

3.        j ← r+1

4.        while TRUE do

a)        Repeat j ← j-1

b)        until A[j] ≤ x

c)        Repeat i ← i+1

d)        until A[i] ≥ x

e)        if i < j

f)         then exchange A[i] ↔ A[j]

g)        else return j

 

void quickSort(int numbers[], int array_size)
    {
      q_sort(numbers, 0, array_size - 1);
    }


    void q_sort(int numbers[], int left, int right)
    {
      int pivot, l_hold, r_hold;

      l_hold = left;
      r_hold = right;
      pivot = numbers[left];
      while (left < right)
      {
        while ((numbers[right] >= pivot) && (left < right))
          right--;
        if (left != right)
        {
          numbers[left] = numbers[right];
          left++;
        }
        while ((numbers[left] <= pivot) && (left < right))
          left++;
        if (left != right)
        {
          numbers[right] = numbers[left];
          right--;
        }
      }
      numbers[left] = pivot;
      pivot = left;
      left = l_hold;
      right = r_hold;
      if (left < pivot)
        q_sort(numbers, left, pivot-1);
      if (right > pivot)
        q_sort(numbers, pivot+1, right);
    }