Finding the Minimum And Maximum in ArrayList w/o Sorting - Java

Question

I am trying to find the Minimum and Maximum Value in an ArrayList without Sorting:

Here is my Current Attempt - However I cannot seem to be getting it to work properly:

import java.util.*;

class Untitled {
    static ArrayList<Integer> al = new ArrayList<Integer>();

    public static void main(String[] args) {

        System.out.println(populateArray(al));
        System.out.println(findMin(al,0));

    }   

    public static ArrayList<Integer> populateArray(ArrayList<Integer> a) {

        al.add(1);
        al.add(2);
        al.add(30);
        al.add(3);
        al.add(13);
        al.add(34);
        al.add(4);
        al.add(3);
        al.add(2);
        al.add(1);
        al.add(93);
        return a;
    }

    public static int findMin(ArrayList<Integer> a, int start) {
        int min = start;

        for(int i=start; i<a.size(); i++) {
            if(a.get(i) < a.get(min)) {
                min = i;
            }
        }
        return start;
    }
}

Could you share with the potential answerers what problems have you found yet? — Gábor Bakos
– Gábor Bakos, Commented May 11, 2015 at 9:21
It means you don't want to use Collections.min and Collections.max. But why? — akhil_mittal
– akhil_mittal, Commented May 11, 2015 at 9:22

Tagir Valeev · Accepted Answer · 2015-05-11 09:27:15Z

2

Using Java 8 you can do this very easily traversing the list only once:

IntSummaryStatistics stats = al.stream().mapToInt(Integer::intValue).summaryStatistics();
System.out.println("Minimum is: "+stats.getMin());
System.out.println("Maximum is: "+stats.getMax());

answered May 11, 2015 at 9:27

Tagir Valeev

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Comments

akhil_mittal · Accepted Answer · 2015-05-11 09:31:53Z

May be you are looking for something like this:

    public static void main(String[] args) {
        findMinMax(new int[] {10,40,50,20,69,37});
    }
    public static void findMinMax(int[] array) {
        if (array == null || array.length < 1)
            return;
        int min = array[0];
        int max = array[0];

        for (int i = 1; i <= array.length - 1; i++) {
            if (max < array[i]) {
                max = array[i];
            }

            if (min > array[i]) {
                min = array[i];
            }
        }
        System.out.println("min: " + min + "\nmax: " + max);
    }

Obviously this is not going to one of the most optimized solution but it will work for you. It uses simple comparison to track min and max values. Output is:

min: 10 max: 69

Sashi Kant · Accepted Answer · 2015-05-11 09:39:35Z

0

You need to do the following::

   public static int findMin(ArrayList<Integer> a) {
            int min = 0;

            for(int i=0; i<a.size(); i++) {
               if(i==0) min= a.get(i);
                if(a.get(i) < min) {
                    min = a.get(i);
                }
            }
            return min;
        } 

public static int findMax(ArrayList<Integer> a) {
        int max = 0;

        for(int i=0; i<a.size(); i++) {
           if(i==0) max= a.get(i);               
           if(a.get(i) > max) {
                max = a.get(i);
            }
        }
        return max;
    }

answered May 11, 2015 at 9:39

Sashi Kant

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