Selection Sort
最后更新于:2022-04-02 01:06:45
# Selection Sort - 选择排序
核心:不断地选择剩余元素中的最小者。
1. 找到数组中最小元素并将其和数组第一个元素交换位置。
1. 在剩下的元素中找到最小元素并将其与数组第二个元素交换,直至整个数组排序。
性质:
- 比较次数=(N-1)+(N-2)+(N-3)+...+2+1~N^2/2
- 交换次数=N
- 运行时间与输入无关
- 数据移动最少
下图来源为 [File:Selection-Sort-Animation.gif - IB Computer Science](http://wiki.ibcsstudent.org/index.php?title=File:Selection-Sort-Animation.gif)
![Selection Sort](https://docs.gechiui.com/gc-content/uploads/sites/kancloud/2015-10-24_562b1f3177b83.gif)
### Implementation
### Python
~~~
#!/usr/bin/env python
def selectionSort(alist):
for i in xrange(len(alist)):
print(alist)
min_index = i
for j in xrange(i + 1, len(alist)):
if alist[j] < alist[min_index]:
min_index = j
alist[min_index], alist[i] = alist[i], alist[min_index]
return alist
unsorted_list = [8, 5, 2, 6, 9, 3, 1, 4, 0, 7]
print(selectionSort(unsorted_list))
~~~
### Java
~~~
public class Sort {
public static void main(String[] args) {
int unsortedArray[] = new int[]{8, 5, 2, 6, 9, 3, 1, 4, 0, 7};
selectionSort(unsortedArray);
System.out.println("After sort: ");
for (int item : unsortedArray) {
System.out.print(item + " ");
}
}
public static void selectionSort(int[] array) {
int len = array.length;
for (int i = 0; i < len; i++) {
for (int item : array) {
System.out.print(item + " ");
}
System.out.println();
int min_index = i;
for (int j = i + 1; j < len; j++) {
if (array[j] < array[min_index]) {
min_index = j;
}
}
int temp = array[min_index];
array[min_index] = array[i];
array[i] = temp;
}
}
}
~~~
### Reference
- [选择排序 - 维基百科,自由的百科全书](http://zh.wikipedia.org/wiki/%E9%80%89%E6%8B%A9%E6%8E%92%E5%BA%8F)
- [The Selection Sort — Problem Solving with Algorithms and Data Structures](http://interactivepython.org/runestone/static/pythonds/SortSearch/TheSelectionSort.html)
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