BOJ 2661 - 좋은수열 [C++]

문제

링크

풀이

#include <iostream>
#include <string>
using namespace std;
 
int n;
 
bool check(string s) {
  int len = s.length();
  for (int i=1; i<=len/2; i++) {
    if (s.substr(len-i, i) == s.substr(len-2*i, i)) return false;
  }
  return true;
}
 
string backtrack(int idx, string s) {
  if (!check(s)) return "";
  if (idx == n) return s;
 
  string ret;
  for (int i=1; i<=3; i++) {
    ret = backtrack(idx+1, s+to_string(i));
    if (ret != "") return ret;
  }
  return "";
}
 
void solve(void) {
  cin >> n;
  cout << backtrack(0, "");
}
 
int main(void) {
  ios::sync_with_stdio(false);
  cin.tie(nullptr);
 
  solve();
  return 0;
}