Submission #1295587

#	Time	Username	Problem	Language	Result	Execution time	Memory
1295587		bakhtiyarn	Palindrome-Free Numbers (BOI13_numbers)	C++20	25 / 100	1 ms	580 KiB

numbers

#include <bits/stdc++.h>
using namespace std;
#define int long long

string a, b; 

int dfs(int i, bool big, bool lit, char last_1, char last_2){
  if(i == b.size()) return 1;
  
  if(big and lit){
    int rest = b.size()-i-1;
    if(last_1 == '%') return 9*pow(8, rest);
    return pow(8, rest+1);
  }
  
  if(lit){
    int cnt = '9'-a[i];
    if(a[i]+1 <= last_1 and last_1 <= '9') cnt--;
    if(a[i]+1 <= last_2 and last_2 <= '9') cnt--;
    if(cnt < 0) cnt = 0;
    
    return cnt * dfs(i+1, true, true, last_2, '9') + dfs(i+1, big, lit, last_2, a[i]);
  }
  if(big){
    int cnt = b[i]-'0';
    if('0' <= last_1 and last_1 <= b[i]-1) cnt--;
    if('0' <= last_2 and last_2 <= b[i]-1) cnt--;
    if(cnt < 0) cnt = 0;
    
    return cnt * dfs(i+1, true, true, last_2, '0') + dfs(i+1, big, lit, last_2, b[i]);
  }
  
  if(a[i] == b[i]) return dfs(i+1, false, false, last_2, a[i]);
  
  int res = 0;
  
  int cnt = b[i]-a[i]-1;
  if(a[i]+1 <= last_1 and last_1 <= b[i]-1) cnt--;
  if(a[i]+1 <= last_2 and last_2 <= b[i]-1) cnt--;
  res += dfs(i+1, true, true, last_2, a[i]+1) * cnt;
    
  if(last_2 != a[i] and last_1 != a[i]) res += dfs(i+1, false, true, last_2, a[i]);
  if(last_2 != b[i] and last_1 != b[i]) res += dfs(i+1, true, false, last_2, b[i]);
  return res;
}

void solve(){
  cin >> a >> b;
  while(a.size() < b.size()) a = '0' + a;
  
  for(int i=0; i<b.size(); i++){
    if(a[i] != b[i]) break;
    if(i and a[i-1] == b[i-1]){
      cout << 0;
      return;
    }
    if(i>1 and a[i-2] == b[i-2] and a[i] == a[i-2]){
      cout << 0;
      return;
    }
  }
  
  cout << dfs(0, false, false, '%', '%') << '\n';
}

signed main() {
  ios_base::sync_with_stdio(0);
  cin.tie(0);
  cout.tie(0);
  solve();
}

• Subtask 1: 5 / 25
• Subtask 2: 20 / 75