Selection Sort，selectionsort_PHP教程

Selection Sort，selectionsort

Red is current min. Yellow is sorted list. Blue is current item. (picture from wikipedia, a little too fast)

10 numbers. Sort as ascend.

1. Find the min of the 10 and switch it with a[0], requires 9 times of compare

2. Find the min of the rest 9 and switch it with a[1], requires 8 times of compare

. . .

1, 10, 9

2, 9, 8

3, 8, 7

4, 7, 6

5, 6, 5

6, 5, 4

7, 4, 3

8, 3, 2

9, 2, 1

In conclusion: For 10 numbers, we need 9 times of finding the min, each has one-short amount of numbers to compare.

Implementation in PHP:

 1 php
 2 /* selection sort: 
 3     1. operate directly on the input array (&), not on a copy
 4     2. sort as ascend
 5 
 6     a is array
 7     m is length of a
 8     n is times of outer loop, which is finding min of the rest
 9     i/j is for-loop counter
10     w is for value swap
11     min is min
12     sub is index of array
13 */
14 function sortSelection(&$a){
15     $m = count($a);
16     $n = $m - 1;
17     $min;
18     $sub;
19     for($i=0; $i$n