Data Structures > Stacks > Poisonous Plants (Javascript)

Hackerrank

'use strict';

const fs = require('fs');

process.stdin.resume();
process.stdin.setEncoding('utf-8');

let inputString = '';
let currentLine = 0;

process.stdin.on('data', function(inputStdin) {
    inputString += inputStdin;
});

process.stdin.on('end', function() {
    inputString = inputString.split('\n');

    main();
});

function readLine() {
    return inputString[currentLine++];
}

/*
 * Complete the 'poisonousPlants' function below.
 *
 * The function is expected to return an INTEGER.
 * The function accepts INTEGER_ARRAY p as parameter.
 */

function poisonousPlants(p) {
    // Write your code here    
    let stacksIndex = 0
    let stacks = p.reduce((pv, cv, ci)=> {
        pv[stacksIndex].push(cv)
        if(cv > p[ci-1]){
            pv.push([])
            stacksIndex++
        }
        return pv
    }, [[]])
    
    if(stacksIndex === 0) return 0
    
    //console.log(`The plants rearranged to stacks: ${JSON.stringify(stacks)}`)
    let days = 0
    while(true){
        // keep last tail ref
        let tailAux = undefined
        
        // if none have removed, than dies stopped
        let stopped = undefined
        for (let i =0; i < stacks.length; i++){
            
            let tail = stacks[i][stacks[i].length -1]
            
            // if the last element have more pesticide, pop it.
            if(stacks[i][stacks[i].length -1] > stacks[i][stacks[i].length -2]){
                stopped = stacks[i].pop()
                
            // if have just an element in the stack
            }else if(stacks[i].length === 1 ){
                // and its bigger than the previous stack tail, pop it
                if(stacks[i] > tailAux){
                  stopped = stacks[i].pop()
                }
            
            // if the last stack tail ref exists, and the actual stack head have more pesticide, shift the current stack head
            }else if(tailAux && stacks[i][0] > tailAux){
                stopped = stacks[i].shift()
            }
            
            // save the last stack tail for ref.
            tailAux = tail
            
        }
        // remove the empty stacks. maybe have some tweak here, filter o(n)
        stacks = stacks.filter( s => s.length > 0)
        
        if(!stopped){ break } else { days ++}
        //console.log(`The plants end of the day ${days} : ${JSON.stringify(stacks)}`)

    }

    return days
}

function main() {
    const ws = fs.createWriteStream(process.env.OUTPUT_PATH);

    const n = parseInt(readLine().trim(), 10);

    const p = readLine().replace(/\s+$/g, '').split(' ').map(pTemp => parseInt(pTemp, 10));

    const result = poisonousPlants(p);

    ws.write(result + '\n');

    ws.end();
}