Detailed quick sort - algorithm implementation notes

First, what is quicksort

Quick Sort Bubble Sort is an improvement

* FIG movable from novice tutorial

Second, implementation

Taken as a reference number of a start number in the number of columns.
Partitioning process, than the large full-count put it right, it is less than or equal to the number of full-put it on the left.
And then the second step is repeated around the interval, until each section is only a number.

Third, the performance parameters on Quick Sort

1, time complexity

Preferably (to be sorted column close disorder): $O(n \log_2 n)$
worst (nearly ordered columns to be sorted): $O (n ^ 2)$
Average: $O(n \log_2 n)$

2, space complexity

$O(n \log_2 n)$

3, is stable

Unstable

4, any suitable type of storage

Sequential storage

Fourth, code implementation

1, for the right to place a large number of reference numbers, eliminate small numbers into the left baseline

There are many ways

As used herein,two pointers

① first A [1] to a temporary storage variable temp, and to make two subscripts left, right end-point to a sequence (e.g., Order left = 1, right = n)

As long as the element pointed right ② A [right] greater than temp, right will continue to the left; when a time A [right] ≤temp when an element A [right] moved to the left pointing element A [left] at.

③ left point as long as the elements A [left] does not exceed temp, will be shifted right and left; when sometime A [left]> temp, the element A [left] moved to the right point to the elements A [right] at .

④ ②③ repeated, until the left and right met, the TEMP (i.e. the original A [1]) into the meet.

Code to achieve this function

// 对于[left,right]区间进行划分
int Partition(int A[], int left, int right){
    int temp = A[left]; //将A[left]存放在temp中
    while(left < right){    // 只要right 与 right不相遇
        while(left < right && A[right] > temp) right--;     //反复左移right
        A[left] = A[right]; 
        while(left < right && A[right] <= temp) right--;     //反复左移right
        A[right] = A[left];
    }
    A[left] = temp; //把temp放到left与right相遇的地方
    return left;    //返回相遇的位置的下标
}

2, quick sort achieve

void quickSort(int A[], int left, int right){
    if(left < right){
        int pos = Partition(A, left, right);
        quickSort(A, left, pos - 1);    //对左子区间递归进行快排
        quickSort(A, pos + 1, right);    //对右子区间递归进行快排

    }
}