排序>>选择排序>>选择排序

List:

0.概念+伪代码+示例分析
1.选择排序实现
2.Question
  1. start

基本概念:

维基百科http://zh.wikipedia.org/wiki/%E9%81%B8%E6%93%87%E6%8E%92%E5%BA%8F

伪代码:

function selectSort(A : list[1..n]) {
    index = n
    while (index > 1): #共有n-1次选择
    {
        max_index = index
        for i from index  downto 1 {  #每次从剩余序列选出最大的
        if(A[i] > A[max_index)
        {
            max_index = i
            }
        }
        swap(A[index], A[max_index ])  #将最大的换到后面
        index = index -1
    }
}

示例:

[49, 38, 65, 97, 76, 13, 27]

Current index 6 value= 27 Max index: 3 value= 97
exchange -> [49, 38, 65, 27, 76, 13, 97]
Current index 5 value= 13 Max index: 4 value= 76
exchange -> [49, 38, 65, 27, 13, 76, 97]
Current index 4 value= 13 Max index: 2 value= 65
exchange -> [49, 38, 13, 27, 65, 76, 97]
Current index 3 value= 27 Max index: 0 value= 49
exchange -> [27, 38, 13, 49, 65, 76, 97]
Current index 2 value= 13 Max index: 1 value= 38
exchange -> [27, 13, 38, 49, 65, 76, 97]
Current index 1 value= 13 Max index: 0 value= 27
exchange -> [13, 27, 38, 49, 65, 76, 97]
Done
  1. start

实现代码

def select_sort(l):
    index = len(l) -1
    while index:
        max_index = index
        for i in range(index):
            if l[i] > l[max_index]:
                max_index = i
        if l[max_index] > l[index]:
            l[index],l[max_index] = l[max_index], l[index]
        index -= 1
  1. start

A.概念,过程描述?

B.交换次数,比较次数,赋值次数?

C. 时间复杂度?空间复杂度?是否是稳定排序?

D.适用场景,何种情况下表现最优