백트랙킹

permutation

function backtracking(depth):
    global answer
    if (base condition) {
        (answer 갱신)
        return
    }
    
    for (i=0; i<len(width); i++) {
    	visited[i] = True
        backtracking(i, depth+1)
        visited[i] = False
    }

combination

function backtracking(start, depth):
    global answer
    if (base condition) {
        (answer 갱신)
        return
    }
    
    for (i=start; i<len(width); i++) {
    	visited[i] = True
        backtracking(i, depth+1)
        visited[i] = False
    }

permutation과 combination을 잘 구분해서 시간초과 안나게 할 것.