[Programmers] Greedy - 체육복 lv1

https://school.programmers.co.kr/learn/courses/30/lessons/42862?language=javascript 

프로그래머스

function solution(n, lost, reserve) {
    var answer = 0;
    
    lost = lost.map((l) => {
       if(reserve.includes(l)) {
           reserve = new Set(reserve);
           reserve.delete(l);
           reserve = Array.from(reserve);
       } else return l;
    });
    
    let borrow = new Array(n).fill().map(n => 0);
    borrow = borrow.map((n, index) => {
        if(reserve.includes(index+1)) {
            return 1;
        } else return 0;
    });
    
    let student = new Array(n).fill().map(n => true);
    student = student.map((n, index) => {
        if(lost.includes(index+1)) {
            return false;
        } else return true;
    });
    
    student.forEach((s, index) => {
        if(!s) { // 체육복 없는 학생
            let left = index -1 < 0 ? null : index -1;
            let right = index +1 >= student.length ? null : index +1;
            
            if(left !== null && borrow[left] === 1) {
                student[index] = true;
                borrow[left] = 0;
            } else if(borrow[right] !== null && borrow[right] === 1) {
                student[index] = true;
                borrow[right] = 0;            
            }
        }
    })

    return student.filter(s => s === true).length;
}