76 lines
2.7 KiB
Markdown
76 lines
2.7 KiB
Markdown
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---
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title: Freecodecamp Algorithm Selection Sort Guide
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---
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The selection sort algorithm sorts an array by repeatedly finding the minimum element (considering ascending order) from the unsorted part and putting it at the beginning. The algorithm maintains two subarrays in a given array.
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1\. The subarray which is already sorted.
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2\. Remaining subarray which is unsorted.
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In every iteration of selection sort, the minimum element (considering ascending order) from the unsorted subarray is picked and moved to the sorted subarray.
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## Example
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<a href='http://www.sorting-algorithms.com/selection-sort' target='_blank' rel='nofollow'>Animation of SelectionSort</a>
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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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#### C++ Implementation
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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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:rocket: [Run Code</a> #### Python Implementation
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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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 <a href='https://repl.it/CXwQ' target='_blank' rel='nofollow'>Run Code</a>
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#### <a href='https://www.freecodecamp.com/videos/big-o-notation-what-it-is-and-why-you-should-care' target='_blank' rel='nofollow'>Complexity of Algorithm</a>
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**Time Complexity:** O(n*n) Due to the two nested loops.
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