[백준][2661] 백트랙킹

https://www.acmicpc.net/problem/2661

2661번: 좋은수열

import sys

def check(res):
    for i in range(1, len(res)//2+1):
        if res[-i*2:-i] == res[-i:]:
            return True
    return False


def backtracking(L, res):
    global result
    if check(res):
        return
    if L == n:
        print(res)
        sys.exit(0)
    else:
        for i in range(3):
            backtracking(L+1, res+ls[i])


if __name__ == "__main__":
    n = int(input())
    print('n :', n)
    ls = ["1", "2", "3"]
    result = 0
    
    for j in range(3):
        backtracking(1, ls[j])