---
title: Freecodecamp Algorithm Selection Sort Guide
localeTitle: Freecodecamp算法选择排序指南
---
选择排序算法通过从未排序部分重复找到最小元素（考虑升序）并将其放在开头来对数组进行排序。该算法在给定数组中维护两个子数组。
1.已经排序的子阵列。
2.剩余的未分类的子阵列。
在选择排序的每次迭代中，挑选来自未排序子阵列的最小元素（考虑升序）并将其移动到排序子阵列。
## 例
[SelectionSort的动画](http://www.sorting-algorithms.com/selection-sort)
```
arr] = 64 25 12 22 11
# Placing the minimum element in arr[0...4] in the beginning
11 25 12 22 64
# Placing the minimum element in arr[1...4] in the beginning
11 12 25 22 64
# Placing the minimum element in arr[2...4] in the beginning
11 12 22 25 64
# Placing the minimum element in arr[3...4] in the beginning
11 12 22 25 64
```
#### C ++实现
```
void selection_sort(int array[], int n)
{
// Contains index of minimum element in unsorted subarray
int min_index;
// Move boundary of unsorted subarray
for(int i = 0; i < n-1; i++)
{
// Find the minimum element in unsorted subarray
min_index = i;
for(int j = i+1; j < n; j++)
{
// If present element is less than element at min_index
// Then change min_index to present index
if(array[j] < array[min_index])
{
min_index = j;
}
}
// Swap the element at min_index with the first element
int temp;
temp = array[min_index];
array[min_index] = array[i];
array[i] = temp;
}
}
```
：rocket：\[运行代码#### Python实现
```
def selection_sort(arr):
for i in range(len(arr)):
min_x = i
for j in range(i+1,len(arr)):
if arrj] < arr[min_x]:
min_x = j
arr[min_x], arr[i] = arr[i], arr[min_x]
arr = [64, 25, 12, 22, 11]
selection_sort(arr)
print(arr) # Prints [11, 12, 22, 25, 64]
```
 [运行代码](https://repl.it/CXwQ)
#### [算法的复杂性](https://www.freecodecamp.com/videos/big-o-notation-what-it-is-and-why-you-should-care)
**时间复杂度：** O（n \* n）由于两个嵌套循环。