A sorting algorithm that slightly improves on selection sort
As we know, selection sort algorithm takes the minimum on every pass on the array, and place it at its correct position.
The idea is to take also the maximum on every pass and place it at its correct position. So in every pass, we keep track of both maximum and minimum and array becomes sorted from both ends.
Examples:
First example: 7 8 5 4 9 2
Input :pass 1:|7 8 5 4 9 2|
pass 2: 2|8 5 4 7|9
pass 3: 2 4|5 7|8 9
Output :A sorted array: 2 4 5 7 8 9
second example: 23 78 45 8 32 56 1
Input :pass 1:|23 78 45 8 32 56 1|
pass 2: 1|23 45 8 32 56 |78
pass 3: 1 8|45 23 32|56 78
pass 4: 1 8 23 |32|45 56 78
in a case of odd elements, so one element
left for sorting, so sorting stops and the
array is sorted.
Output : A sorted array: 1 8 23 32 45 56 78
C++
// C++ program to implement min max selection // sort. #include <iostream> using namespace std; void minMaxSelectionSort(int* arr, int n) { for (int i = 0, j = n - 1; i < j; i++, j--) { int min = arr[i], max = arr[i]; int min_i = i, max_i = i; for (int k = i; k <= j; k++) { if (arr[k] > max) { max = arr[k]; max_i = k; } else if (arr[k] < min) { min = arr[k]; min_i = k; } } // shifting the min. swap(arr[i], arr[min_i]); // Shifting the max. The equal condition // happens if we shifted the max to arr[min_i] // in the previous swap. if (arr[min_i] == max) swap(arr[j], arr[min_i]); else swap(arr[j], arr[max_i]); } } // Driver code int main() { int arr[] = { 23, 78, 45, 8, 32, 56, 1 }; int n = sizeof(arr) / sizeof(arr[0]); minMaxSelectionSort(arr, n); printf("Sorted array:\n"); for (int i = 0; i < n; i++) cout << arr[i] << " "; cout << endl; return 0; } |
Java
// Java program to implement min max selection // sort. class GFG { static void minMaxSelectionSort(int[] arr, int n) { for (int i = 0, j = n - 1; i < j; i++, j--) { int min = arr[i], max = arr[i]; int min_i = i, max_i = i; for (int k = i; k <= j; k++) { if (arr[k] > max) { max = arr[k]; max_i = k; } else if (arr[k] < min) { min = arr[k]; min_i = k; } } // shifting the min. swap(arr, i, min_i); // Shifting the max. The equal condition // happens if we shifted the max to arr[min_i] // in the previous swap. if (arr[min_i] == max) swap(arr, j, min_i); else swap(arr, j, max_i); } } static int[] swap(int []arr, int i, int j) { int temp = arr[i]; arr[i] = arr[j]; arr[j] = temp; return arr; } // Driver code public static void main(String[] args) { int arr[] = { 23, 78, 45, 8, 32, 56, 1 }; int n = arr.length; minMaxSelectionSort(arr, n); System.out.printf("Sorted array:\n"); for (int i = 0; i < n; i++) System.out.print(arr[i] + " "); System.out.println(""); } } // This code is contributed by Princi Singh |
Python3
# Python 3 program to implement min # max selection sort. def minMaxSelectionSort(arr, n): i = 0 j = n - 1 while(i < j): min = arr[i] max = arr[i] min_i = i max_i = i for k in range(i, j + 1, 1): if (arr[k] > max): max = arr[k] max_i = k elif (arr[k] < min): min = arr[k] min_i = k # shifting the min. temp = arr[i] arr[i] = arr[min_i] arr[min_i] = temp # Shifting the max. The equal condition # happens if we shifted the max to # arr[min_i] in the previous swap. if (arr[min_i] == max): temp = arr[j] arr[j] = arr[min_i] arr[min_i] = temp else: temp = arr[j] arr[j] = arr[max_i] arr[max_i] = temp i += 1 j -= 1 print("Sorted array:", end = " ") for i in range(n): print(arr[i], end = " ") # Driver code if __name__== '__main__': arr = [23, 78, 45, 8, 32, 56, 1] n = len(arr) minMaxSelectionSort(arr, n) # This code is contributed by # Surendra_Gangwar |
C#
// C# program to implement min max selection // sort. using System; class GFG { static void minMaxSelectionSort(int[] arr, int n) { for (int i = 0, j = n - 1; i < j; i++, j--) { int min = arr[i], max = arr[i]; int min_i = i, max_i = i; for (int k = i; k <= j; k++) { if (arr[k] > max) { max = arr[k]; max_i = k; } else if (arr[k] < min) { min = arr[k]; min_i = k; } } // shifting the min. swap(arr, i, min_i); // Shifting the max. The equal condition // happens if we shifted the max to arr[min_i] // in the previous swap. if (arr[min_i] == max) swap(arr, j, min_i); else swap(arr, j, max_i); } } static int[] swap(int []arr, int i, int j) { int temp = arr[i]; arr[i] = arr[j]; arr[j] = temp; return arr; } // Driver code public static void Main(String[] args) { int []arr = { 23, 78, 45, 8, 32, 56, 1 }; int n = arr.Length; minMaxSelectionSort(arr, n); Console.Write("Sorted array:\n"); for (int i = 0; i < n; i++) Console.Write(arr[i] + " "); Console.WriteLine(""); } } // This code is contributed by Rajput-Ji |
Output:
Sorted array: 1 8 23 32 45 56 78
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