Implement a java program to find the smallest distance between two neighbouring numbers in an array.

Here is the JAVA program to find smallest distance between 2 neighboring numbers in an array.

import java.lang.Math; // for importing Math class functions

import java.util.Scanner; // for importing Scanner class

public class CalSmallestDistance // class to calculate smallest distance

{public static void main(String[] args) {     // to enter java program

    Scanner s = new Scanner(System.in);  //creating scanner object

    int size; // size of the array

  System.out.print("Enter size of the array:"); //prompts to enter array size

       size = s.nextInt(); // reads input

       int arr[] = new int[size];  // array named arr[]

      //line below prompts to enter elements in the array             System.out.println("Enter numbers in the array:");

       for(int j = 0; j < size; j++)        //loops through the array

           {arr[j] = s.nextInt(); }     //reads the input elements

      int smallest_distance = Math.abs(arr[0]-arr[1]);  

       int position= 0; //index of the array

       for(int i=1; i<arr.length-1; i++){

           int distance= Math.abs(arr[i]-arr[i+1]);

           if(distance< smallest_distance){

           smallest_distance= distance;

           position = i;            }        }

  System.out.println("Smallest distance is :"+smallest_distance);

System.out.println("The numbers are  :"+arr[position]+ " and " +arr[position+1]);      } }

I have stated the minor explanation of some basic lines of code as comments in the code given above.

Now i will give the detailed explanation about the working of the main part of the code.

Lets start from here

      int smallest_distance = Math.abs(arr[0]-arr[1]);  

In this statement the array element at 0 index (1st position) and the array element at 1 index (2nd position) of the array are subtracted.

Then i used the math.abs() method here  which gives absolute value

Lets say the distance between 3 and 5 is -2 as 3-5 equals to -2. But the math.abs() method will return 2 instead of -2.

Now the subtraction of two array elements and absolute value (if subtraction result is negative) will be assigned to variable smallest_distance.

       for(int i=1; i<arr.length-1; i++)

This is for loop. Variable i is positioned to the 1 index of the array (arr) (it is pointing to the second element of the array). It will move through the array until the end of the array is reached i.e. the loop will continue till value of i remains less than the length of the array.

Now at the start of the loop body the following statement is encountered

           int distance= Math.abs(arr[i]-arr[i+1]);

This subtracts the array element at i th position and array element at i th +1 position (means one position ahead of array element at i th position). In simple words two neighboring numbers in an array are being subtracted and Math.abs() method is used to give absolute value. The result of this operation is assigned to distance variable.

           if(distance< smallest_distance)

This if statement checks if the value in distance variable is smallest than the value of smallest_distance variable which was previously calculated before calculating the value for distance variable.

If this condition is true then the following statements are executed:

             smallest_distance= distance;

if distance value is less than value in smallest_distance, then the value of distance is assigned to smallest_distance.

this means the smallest_distance will keep on storing the smallest distance between two neighboring numbers.

Next the value of variable i that is pointing to the 1st index of the array is now assigned to the position variable.

                                         position = i;

It will keep assigning the value of i to position variable so at the end of the program we can get the positions of the two neighboring numbers that have the smallest distance between them.

Then the value of i is incremented and moves one place ahead in the array.

Then the 2nd iteration takes place and again checks if i pointer variable has reached the end of the array. If not the loop body will continue to execute in which the distance between the two neighboring numbers is calculated and shortest distance is stored in smallest_distance.

When i reaches the end of the array the loop will break and the smallest distance between two neighboring numbers in the array have been stored in the smallest_distance variable.

Finally the statement System.out.println("Smallest distance is :"+smallest_distance); displays the shortest distance and the statement System.out.println("The numbers are  :"+arr[position]+ " and " +arr[position+1]); displays the array index positions at which the two neighboring numbers have the smallest distance.

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