This tutorial provides Java solution to "Jumping on the Clouds" challenge of HackerRank.

Hackerrank Challenge Details

Problem Statement:

Emma is playing a new mobile game involving n clouds numbered from 0 to n - 1. A player initially starts out on cloud c₀, and they must jump to cloud c_n-1. In each step, she can jump from any cloud  to cloud  or cloud .

There are two types of clouds, ordinary clouds and thunderclouds. The game ends if Emma jumps onto a thundercloud, but if she reaches the last cloud (i.e., c_n-1), she wins the game!

Can you find the minimum number of jumps Emma must make to win the game? It is guaranteed that clouds c₀ and c_n-1 are ordinary-clouds and it is always possible to win the game.

Input Format:

The first line contains an integer, n (the total number of clouds). 
The second line contains n space-separated binary integers describing clouds c₀, c₁, c₂,..., c_n-1.

• If c_i = 0, the i^th cloud is an ordinary cloud.
• If c_i = 1, the i_th cloud is a thundercloud.

Output Format:

Print the minimum number of jumps needed to win the game.

Constraints:

• 2 < n < 100
• ci € {0, 1}
• c₀ = c_n-1 = 0

Sample Input 0:

7
0 0 1 0 0 1 0

Sample Output 0:

4

Sample Input 1:

6
0 0 0 0 1 0

Sample Output 1:

3

Explanation:

Sample Case 0: 
Because c₂ and c₅ in our input are both 1, Emma must avoid c₂ and c₅. Bearing this in mind, she can win the game with a minimum of 4 jumps:

Sample Case 1: 
The only thundercloud to avoid is c₄. Emma can win the game in 3 jumps:

Solution Details

Java Implementation:

package com.saintech.allprogtutorials.hackerrank.algos;

import java.util.Scanner;

/**
 * @author Sain Technology Solutions
 * 
 * Solution to Problem - https://www.hackerrank.com/challenges/jumping-on-the-clouds
 *
 */
public class JumpingOnClouds {
	
	public static void main(String[] args) {
		final Scanner in = new Scanner(System.in);
		final int N = in.nextInt();
		
		// Put all the clouds in an array
		final int[] clouds = new int[N];
		for(int i = 0; i < N; i++) {
			clouds[i] = in.nextInt();
		}
		
		// Check if two steps can be taken by verifying cloud type at 
		// second step. Otherwise check if one step can be taken by verifying 
		// if we still have any more clouds. If none of these conditions are met,
		// break out of infinite loop.
		int noOfJumps = 0, i = 0;
		while(true) {
			if(i + 2 < N && clouds[i + 2] == 0) {
				i += 2;
			} else if(i + 1 < N) {
				i++;
			} else {
				break;
			}
			noOfJumps++;
		}
		
		System.out.println(noOfJumps);
		
		in.close();
	}

}

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