python 选择排序

1 a = [9,1,22,31,45,3,6,2,11]
3 for i in range(len(a)-1):
4     index = i                                   #index标记最小的 值  假设第一个是最小的值
5     for j in range(i+1,len(a)):
6         if a[index] > a[j]: 
7             index = j                           #index 一直指向最小的值
8     a[i],a[index] = a[index],a[i]               #让a[index]  与  第[i]个值 互换  ，达到排序
9 print(a)
输出结果：[1, 2, 3, 6, 9, 11, 22, 31, 45]

过程：

[9, 1, 22, 31, 45, 3, 6, 2, 11]
[1, 9, 22, 31, 45, 3, 6, 2, 11]
[1, 2, 22, 31, 45, 3, 6, 9, 11]
[1, 2, 3, 31, 45, 22, 6, 9, 11]
[1, 2, 3, 6, 45, 22, 31, 9, 11]
[1, 2, 3, 6, 9, 22, 31, 45, 11]
[1, 2, 3, 6, 9, 11, 31, 45, 22]
[1, 2, 3, 6, 9, 11, 22, 45, 31]
[1, 2, 3, 6, 9, 11, 22, 31, 45]