How to resolve this selection sort in ArrayList

Question

I am implementing Selection Sort Algorithm in java using ArrayList. Algorithm I implemented is correct but I am not getting valid output. can anyone help me please if I am going wrong with this Arraylist. code :

import java.util.*;
public class SelectionSort {
public static void main(String[] args) {
    ArrayList <Integer> array = new ArrayList<Integer>();
    array.add(50);
    array.add(30);
    array.add(10);
    array.add(60);
    array.add(40);
    System.out.println(array);
    selsort(array);

}
private static ArrayList<Integer> selsort(ArrayList<Integer> array){
    int i = 0;
    int imin = 0;
    int len = array.size();
    for (i = 0;i <len-1; i++){
        imin = i;
        for (int j = i+1; j<len; j++) {
            if ((Integer) (array.get(j)) < (Integer) (array.get(imin))){
                    imin = j;
            }
            Collections.swap(array,i,j);
        }
    }
    System.out.println(array);
    return array;

}
}

output :

[50, 30, 10, 60, 40] //before
[40, 60, 10, 30, 50] //after

luk2302 · Accepted Answer · 2017-01-22 12:31:32Z

2

You are swapping the elements with the wrong indices in the wrong place.
The correct swap is i with imin.
The correct place is outside the inner loop:

private static ArrayList<Integer> selsort(ArrayList<Integer> array){
    int i = 0;
    int len = array.size();
    for (i = 0; i < len - 1; i++) {
        int imin = i;
        for (int j = i + 1; j < len; j++) {
            if (array.get(j) < array.get(imin)) {
                imin = j;
            }
        }
        Collections.swap(array,i,imin);      
    }
    System.out.println(array);
    return array;
}

[50, 30, 10, 60, 40]
[10, 30, 40, 50, 60]

answered Jan 22, 2017 at 12:31

luk2302

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2 Comments

luk2302 Over a year ago

@minigeek you are welcome. Yes I did remove the casting since it is not needed because you have a generic ArrayList which ensures that whatever you take out is an Integer anyway.

minigeek Over a year ago

it was showing me error before..donno why..now it isn't

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