개발야옹

https://school.programmers.co.kr/learn/courses/30/lessons/120922

function solution(M, N) {
    var answer = 0;
    if(M === 1 && N === 1) return 0;
    
    return (M*N)-1;
}

https://school.programmers.co.kr/learn/courses/30/lessons/86491

function solution(sizes) {
    var answer = 0;
    sizes.forEach((s) => {
        if(s[1] > s[0]) {
            let tmp = s[0];
            s[0] = s[1];
            s[1] = tmp;
        };
    });
    
    const w = [];
    const h = [];    
    
    for(let i = 0; i < sizes.length ; i ++) {
        w.push(sizes[i][0]);
        h.push(sizes[i][1]);
    }
    
    answer = Math.max(...w);
    answer *= Math.max(...h);
    
    return answer;
}

https://school.programmers.co.kr/learn/courses/30/lessons/120812

function solution(array) {
    // 최빈값 여러개면 -1 리턴
    if(array.length === 1){
        return array[0];
    }
    
    const obj = {};
    array.forEach((a) => {
       if(obj[a] === undefined) obj[a] = 1;
        else obj[a] += 1;
    });
    
    const keyList = Object.keys(obj);
    let cnt = 1;
    let max = -1;
    let answer = '';
    keyList.forEach(key => {
        if(max === obj[key]) {
            cnt ++;
        }
        if(max < obj[key]) {
            max = obj[key];
            answer = key;
            cnt = 1;
        }
    });
        
    
    return cnt > 1 ? -1 : Number(answer);
}

https://school.programmers.co.kr/learn/courses/30/lessons/120861

function solution(keyinput, board) {
    var answer = [0,0];
    const x = Math.floor(board[0]/2);
    const y = Math.floor(board[1]/2);
    
    keyinput.forEach((k) => {
        if(k === "up") {
            if(answer[1] < y) answer[1] += 1;
        }
        else if(k === "down") {
            if(answer[1] > y*-1) answer[1] -= 1;
        }
        else if(k === "right") {
            if(answer[0] < x ) answer[0] += 1;
        }
        else {
            if(answer[0] > x*-1) answer[0] -= 1;
        }
    });
    
    return answer;
}