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Java Exercises: Create and display unique three-digit number using 1, 2, 3, 4. Also count how many three-digit numbers are there

Java Basic: Exercise-39 with Solution

Write a Java program to create and display unique three-digit number using 1, 2, 3, 4. Also count how many three-digit numbers are there.

Pictorial Presentation:

Java: Create and display unique three-digit number using 1, 2, 3, 4.

Sample Solution:

Java Code:

import java.util.Scanner;

public class Exercise39 {
    
 public static void main(String[] args) {
		int amount = 0;
		for(int i = 1; i <= 4; i++){
			for(int j = 1; j <= 4; j++){
				for(int k = 1; k <= 4; k++){
					if(k != i && k != j && i != j){
						amount++;
						System.out.println(i + "" + j + "" + k);
					}
				}
			}
		}
		System.out.println("Total number of the three-digit-number is " + amount);
	}
}

Sample Output:

123                                                                                                      
124                                                                                                      
132                                                                                                      
134                                                                                                      
142                                                                                                      
143                                                                                                      
213                                                                                                      
214                                                                                                      
231                                                                                                      
234                                                                                                      
241  
------
431                                                                                                      
432                                                                                                      
Total number of the three-digit-number is 24 

Flowchart:

Flowchart: Java exercises: Create and display unique three-digit number

Java Code Editor:

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Java: Tips of the Day

How to detect a loop in a linked list?

You can make use of Floyd's cycle-finding algorithm, also known as tortoise and hare algorithm.

The idea is to have two references to the list and move them at different speeds. Move one forward by 1 node and the other by 2 nodes.

  • If the linked list has a loop they will definitely meet.
  • Else either of the two references(or their next) will become null.

Java function implementing the algorithm:

boolean hasLoop(Node first) {

    if(first == null) // list does not exist..so no loop either
        return false;

    Node slow, fast; // create two references.

    slow = fast = first; // make both refer to the start of the list

    while(true) {

        slow = slow.next;          // 1 hop

        if(fast.next != null)
            fast = fast.next.next; // 2 hops
        else
            return false;          // next node null => no loop

        if(slow == null || fast == null) // if either hits null..no loop
            return false;

        if(slow == fast) // if the two ever meet...we must have a loop
            return true;
    }
}

Ref: https://bit.ly/2P6SCq4