Finding out the minimum difference between elements in an array

Question

I have an integer array with some finite number of values. My job is to find the minimum difference between any two elements in the array.

Consider that the array co

Answer 1

This is actually a restatement of the closest-pair problem in one-dimension. https://en.wikipedia.org/wiki/Closest_pair_of_points_problem http://www.cs.umd.edu/~samir/grant/cp.pdf

As the Wikipedia article cited below points out, the best decision-tree model of this problem also runs in Ω(nlogn) time.

Answer 2

The given problem can easily be solved in O(n) time. Look at the following code that I wrote.

    import java.util.Scanner;
    public class Solution {
    public static void main(String [] args) {
        Scanner input = new Scanner(System.in);
        int i, minDistance = 999999;
        boolean flag = false;
        int capacity = input.nextInt();
        int arr[] = new int[capacity];
        for (i = 0; i < capacity; i++) {
            arr[i] = input.nextInt();
        }

        int firstElement = input.nextInt();
        int secondElement = input.nextInt();

        int prev = 0;

        for (i = 0; i < capacity; i++) {
            if (arr[i] == firstElement || arr[i] == secondElement) {
                prev = i;
                break;
            }
        }

        for (; i < capacity; i++) {
            if(arr[i] == firstElement || arr[i] == secondElement) {
                if(arr[i] != arr[prev] && minDistance > Math.abs(i - prev)) {
                    minDistance = Math.abs(i - prev);
                    flag = true;
                    prev = i;
                } else {
                    prev = i;
                }
            }
        }

        if(flag)
            System.out.println(minDistance);
        else
            System.out.println("-1");
    }
}