【选择排序】直接选择排序
前言
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思想
比如，以下是未排序的数组：
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| 4 | 3 | 5 | 1 | 2 |
经过第1轮选择，找出最小值，放第1位
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int temp = arr[0]
arr[1] < temp -> temp = arr[1]
| 4 | 3 | 5 | 1 | 2 |
↑ ↑
arr[2] > temp -> temp
| 4 | 3 | 5 | 1 | 2 |
↑
arr[3] < temp -> temp = arr[3]
| 4 | 3 | 5 | 1 | 2 |
↑
arr[4] > temp -> temp
| 4 | 3 | 5 | 1 | 2 |
↑
arr[3] = arr[0],arr[0] = temp
| 1 | 3 | 5 | 4 | 2 |
继续第2轮选择，找出除首位外的最小值，放第2位
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int temp = arr[1]
arr[2] > temp -> temp;
| 1 | 3 | 5 | 4 | 2 |
↑ ↑
arr[3] > temp -> temp;
| 1 | 3 | 5 | 4 | 2 |
↑
arr[4] < temp -> temp = arr[4]
| 1 | 3 | 5 | 4 | 2 |
↑
arr[4] = arr[1] arr[1] = temp
| 1 | 2 | 5 | 4 | 3 |
继续第三轮选择，在未排序序列中找出最小值放第3位
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int temp = arr[2];
arr[3] < temp -> temp = arr[3]
| 1 | 2 | 5 | 4 | 3 |
↑ ↑
arr[4] < temp -> temp =arr[4]
| 1 | 2 | 5 | 4 | 3 |
↑
arr[4] = arr[2] arr[2] = temp
| 1 | 2 | 3 | 4 | 5 |
继续第4轮选择，在未排序序列中找最小值放第4位
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int temp = arr[3]
arr[4] > temp -> temp
| 1 | 2 | 3 | 4 | 5 |
↑ ↑
arr[3] = temp
| 1 | 2 | 3 | 4 | 5 |
Code
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public class Demo{
public static void main(String[] args){
int[] arr = {10,7,9,1,8,5,2};
bubbleSort(arr);
}
public static void selectSort(int[] arr){
int arrLength = arr.length;
for(int i=0; i<arrLength; i++){
int temp = arr[i];
int position = i;
for(int j=i+1; j< arrLength; j++){
if( arr[j] < temp ){
temp = arr[j];
position = j;
}
}
arr[position] = arr[i];
arr[i] = temp;
}
}
}
本篇所属：算法篇