Sorting an array using Selection Sort

Question

I have implemented a code to sort this array using Selection Sort. The code seems to be fine, but it doesn't sort the array perfectly. This is the array to be sorted, {20, 46, 22, 19, 6, 42, 14, 5, 48, 47, 17, 39, 51, 7, 2}

Here is the code I implemented;

public class Main {

    public static void main(String[] args) {
        int[] arr = {20, 46, 22, 19, 6, 42, 14, 5, 48, 47, 17, 39, 51, 7, 2};
        System.out.println("Unsorted Array: \t");
        StringBuffer sb = new StringBuffer();
        for (Object s : arr) {
            sb.append(s);
            sb.append(" ");
        }
        String str = sb.toString();
        System.out.println(str);


        selectionSort(arr);
        System.out.println("Sorted Array: \t");
        printArray(arr);
    }

    public static void selectionSort(int[] arr) {
        int n = arr.length;
        // one by one move boundary of unsorted subarray
        for (int i = 0; i < n - 1; i++) {
            // find the minimum element in unsorted array
            int min = i;
            for (int j = i + 1; j < n; j++) {
                if (arr[j] < arr[min]) {
                    min = j;
                }
                //swapping the found min value with the first element
                int temp = arr[min];
                arr[min] = arr[i];
                arr[i] = temp;
            }
        }
    }

    public static void printArray(int[] arr) {
        StringBuffer sb = new StringBuffer();
        for (Object s : arr) {
            sb.append(s);
            sb.append(" ");
        }
        String str = sb.toString();
        System.out.println(str);
    }
}

And here is the output I received;

I have no idea why it is not sorting out properly, Would love to have some help.

Elliott Frisch · Accepted Answer · 2021-09-04 18:10:11Z

1

The swap comes after the inner loop. Like,

public static void selectionSort(int[] arr) {
    int n = arr.length;
    // one by one move boundary of unsorted subarray
    for (int i = 0; i < n - 1; i++) {
        // find the minimum element in unsorted array
        int min = i;
        for (int j = i + 1; j < n; j++) {
            if (arr[j] < arr[min]) {
                min = j;
            }
        }
        // swapping the found min value with the first element
        int temp = arr[min];
        arr[min] = arr[i];
        arr[i] = temp;
    }
}

Just changing that (and adding a printArray) I get

Unsorted Array:     
[20, 46, 22, 19, 6, 42, 14, 5, 48, 47, 17, 39, 51, 7, 2]
Sorted Array:   
[2, 5, 6, 7, 14, 17, 19, 20, 22, 39, 42, 46, 47, 48, 51]

answered Sep 4, 2021 at 18:10

Elliott Frisch

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Comments

alok singh · Accepted Answer · 2023-10-11 07:43:25Z

0

class selecion_sort{
    static void selection(int[] arr){
        for (int i=0;i<arr.length-1;++i){
//initialise the element to a variable named 'key' and traverse the element
//using another for loop and compare the the smallest number among the elements 
//of the array.... 
            int key=i;
            for (int j=i+1;j<arr.length;++j){
                if (arr[key]>arr[j]){
                    key=j;                                                         
                }
            }
//swap the smallest element with the first element and as the iteration grows 
//the swapping continues as 1st,2nd,3rd elements.......
            int temp=arr[key];
            arr[key]=arr[i];
            arr[i]=temp;
        }
    }                     
//this method prints the elements of an array.....                                                     
    static void print(int[] arr){
        for (int i=0;i<arr.length;++i){
            System.out.print(" "+arr[i]);
        }
    }
    public static void main(String[] args){
        int[] arr={23,54,65,12,87,45,10,45};
     selection(arr);
    print(arr);
    }
}

answered Oct 11, 2023 at 7:43

alok singh

11 bronze badge

2 Comments

greybeard Over a year ago

This does not answer why [is the code presented] not sorting out properly?

alok singh Over a year ago

please elaborate........

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