In the selection sort technique, the list is divided into two parts. In one part all elements are sorted and in another part the items are unsorted. At first, we take the maximum or minimum data from the array. After getting the data (say minimum) we place it at the beginning of the list by replacing the data of first place with the minimum data. After performing the array is getting smaller. Thus this sorting technique is done.
The complexity of Selection Sort Technique
- Time Complexity: O(n^2)
- Space Complexity: O(1)
Input and Output
Input: The unsorted list: 5 9 7 23 78 20 Output: Array before Sorting: 5 9 7 23 78 20 Array after Sorting: 5 7 9 20 23 78
Algorithm
selectionSort(array, size)
Input − An array of data, and the total number in the array
Output − The sorted Array
Begin for i := 0 to size-2 do //find minimum from ith location to size iMin := i; for j:= i+1 to size – 1 do if array[j] < array[iMin] then iMin := j done swap array[i] with array[iMin]. done End
Example
#include<iostream>
using namespace std;
void swapping(int &a, int &b) { //swap the content of a and b
int temp;
temp = a;
a = b;
b = temp;
}
void display(int *array, int size) {
for(int i = 0; i<size; i++)
cout << array[i] << " ";
cout << endl;
}
void selectionSort(int *array, int size) {
int i, j, imin;
for(i = 0; i<size-1; i++) {
imin = i;//get index of minimum data
for(j = i+1; j<size; j++)
if(array[j] < array[imin])
imin = j;
//placing in correct position
swap(array[i], array[imin]);
}
}
int main() {
int n;
cout << "Enter the number of elements: ";
cin >> n;
int arr[n]; //create an array with given number of elements
cout << "Enter elements:" << endl;
for(int i = 0; i<n; i++) {
cin >> arr[i];
}
cout << "Array before Sorting: ";
display(arr, n);
selectionSort(arr, n);
cout << "Array after Sorting: ";
display(arr, n);
}Output
Enter the number of elements: 6 Enter elements: 5 9 7 23 78 20 Array before Sorting: 5 9 7 23 78 20 Array after Sorting: 5 7 9 20 23 78