80 lines
2.5 KiB
Markdown
80 lines
2.5 KiB
Markdown
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---
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title: Freecodecamp Algorithm Selection Sort Guide
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localeTitle: Freecodecamp算法选择排序指南
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---
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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。
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1.已经排序的子阵列。
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2.剩余的未分类的子阵列。
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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。
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## 例
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[SelectionSort的动画](http://www.sorting-algorithms.com/selection-sort)
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```
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arr<a href='https://repl.it/CZa0' target='_blank' rel='nofollow'>] = 64 25 12 22 11
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# Placing the minimum element in arr[0...4] in the beginning
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11 25 12 22 64
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# Placing the minimum element in arr[1...4] in the beginning
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11 12 25 22 64
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# Placing the minimum element in arr[2...4] in the beginning
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11 12 22 25 64
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# Placing the minimum element in arr[3...4] in the beginning
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11 12 22 25 64
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```
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#### C ++实现
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```
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void selection_sort(int array[], int n)
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{
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// Contains index of minimum element in unsorted subarray
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int min_index;
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// Move boundary of unsorted subarray
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for(int i = 0; i < n-1; i++)
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{
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// Find the minimum element in unsorted subarray
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min_index = i;
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for(int j = i+1; j < n; j++)
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{
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// If present element is less than element at min_index
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// Then change min_index to present index
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if(array[j] < array[min_index])
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{
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min_index = j;
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}
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}
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// Swap the element at min_index with the first element
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int temp;
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temp = array[min_index];
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array[min_index] = array[i];
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array[i] = temp;
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}
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}
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```
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:rocket:\[运行代码#### Python实现
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```
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def selection_sort(arr):
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for i in range(len(arr)):
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min_x = i
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for j in range(i+1,len(arr)):
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if arr<a href='https://forum.freecodecamp.com/images/emoji/emoji_one/rocket.png?v=3 ":rocket:"' target='_blank' rel='nofollow'>j] < arr[min_x]:
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min_x = j
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arr[min_x], arr[i] = arr[i], arr[min_x]
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arr = [64, 25, 12, 22, 11]
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selection_sort(arr)
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print(arr) # Prints [11, 12, 22, 25, 64]
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```
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![:rocket:](https://forum.freecodecamp.com/images/emoji/emoji_one/rocket.png?v=3 ":火箭:") [运行代码](https://repl.it/CXwQ)
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#### [算法的复杂性](https://www.freecodecamp.com/videos/big-o-notation-what-it-is-and-why-you-should-care)
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**时间复杂度:** O(n \* n)由于两个嵌套循环。
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