Array Manipulations and Cyclical Simulation with JavaScript | CodeSignal Learn

Array Manipulations and Cyclical Simulation with JavaScript | CodeSignal Learn

Introduction

Welcome! Are you ready to embark on a captivating journey into the world of array manipulations ? Today, we're going to explore a fascinating scenario involving a wonderful small town, its houses, and a fun balloon game. Without further ado, let's dive right in!

Task Statement

Picture a quaint, small town where every house is numbered sequentially from 1 to n . One day, a festive town event is held, and balloons are tied to each house. The festivities do not end there. At the conclusion of the event, a fun game is played: At each step of the game, each house sends half of its balloons to the neighboring house simultaneously (the neighbor to the right side, and for the last house, the neighbor is the first house). When counting the half of the balloons, we consider the existing balloons before receiving any balloons from a neighbor. The game goes on until, at some step, there are no changes in the number of balloons compared to the previous step. The task is to create a JavaScript function, function solution(balloons), where balloons is an array representing the number of balloons at each house. The function should simulate this game and return the number of steps in the game. For example, if balloons = [4, 1, 2], the output should be solution(balloons) = 3 . After the first step, the list becomes [3, 3, 1] . This is because the first house sends 2 balloons and gets 1, the second house sends nothing but gets 2, and the third house sends 1 but receives nothing. Note that when the number of balloons x is odd, then the house sends (x - 1) / 2 balloons. After the second step, the list becomes [2, 3, 2] and never changes after that. So after the third step, the process finishes.

Solution Building: Step 1 - Understanding the Problem

Firstly, it's essential to note that we're dealing with a cyclical event . In other words, when iterating over our balloons array, we need to perceive the array as circular, meaning balloons[n - 1] should refer back to balloons[0] . This concept of cyclicity becomes crucial when we consider the last house passing balloons to the first.

Solution Building: Step 2 - Setting Up the Loop

Confident in our understanding of the problem, we move on to programming our solution. First, we need to set up a loop to iterate through the rounds of balloon sharing. This loop should continue as long as the array changes. JavaScript function solution(balloons) {const n = balloons.length; let steps = 0; while (true) {steps += 1; let newBalloons = balloons.slice(); // Store updated balloon counts // TODO: Share the balloons if (JSON.stringify(newBalloons) === JSON.stringify(balloons)) {break;} balloons = newBalloons; // Update balloons with new counts.} return steps;} const balloons = [4, 1, 2]; console.log(solution(balloons)); // Output should be 3

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Solution Building: Step 3 - Sharing Balloons

Our next step delves into the core game mechanics: sharing the balloons. Throughout each cycle, each house must share half of its balloons with the next house. We must also ensure that the last house shares balloons with the first house at the end of each cycle — for this, we'll use the modulo % operator. Here's the updated solution, complete with the mechanics of balloon sharing: function solution(balloons) {const n = balloons.length; let steps = 0; while (true) {steps += 1; let newBalloons = balloons.slice(); // Store updated balloon counts for (let i = 0; i < n; i++) {let share = Math.floor(balloons[i] / 2); // Balloons to share newBalloons[i] -= share; // Decrease balloons of current house newBalloons[(i + 1) % n] += share; // Increase balloons of next house} if (JSON.stringify(newBalloons) === JSON.stringify(balloons)) {break;} balloons = newBalloons.slice(); // Update balloons with new counts.} return steps;} const balloons = [4, 1, 2]; console.log(solution(balloons)); // Output should be 3

JavaScript

function solution(balloons) {
    const n = balloons.length;
    let steps = 0;
    while (true) {
        steps += 1;
        let newBalloons = balloons.slice();  // Store updated balloon counts
        for (let i = 0; i < n; i++) {
            let share = Math.floor(balloons[i] / 2);  // Balloons to share
            newBalloons[i] -= share;  // Decrease balloons of current house
            newBalloons[(i + 1) % n] += share;  // Increase balloons of next house
        }
        if (JSON.stringify(newBalloons) === JSON.stringify(balloons)) {
            break;
        }
        balloons = newBalloons.slice();  // Update balloons with new counts.
    }
    return steps;
}

const balloons = [4, 1, 2];
console.log(solution(balloons));  // Output should be 3