Submission #1295604

#	Time	Username	Problem	Language	Result	Execution time	Memory
1295604		bakhtiyarn	Palindrome-Free Numbers (BOI13_numbers)	C++20	73.75 / 100	1 ms	588 KiB

numbers

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

int eight[100];
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*eight[rest];
    return eight[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' and last_1 != last_2) 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 and last_1 != last_2) 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(lit){
    int res = 0;
    for(char j=a[i]+1; j<='9'; j++){
      if(j == last_1 or j == last_2) continue;
      res += dfs(i+1, true, true, last_2, j);
    }
    
    if(a[i] != last_2 and a[i] != last_1) res += dfs(i+1, big, lit, last_2, a[i]);
    return res;
  }
  if(big){
    int res = 0;
    for(char j='0'; j<b[i]; j++){
      if(j == last_1 or j == last_2) continue;
      res += dfs(i+1, true, true, last_2, j);
    }
    
    if(b[i] != last_2 and b[i] != last_1) res += dfs(i+1, big, lit, last_2, b[i]);
    return res;
  }
  
  if(a[i] == b[i]) {
    if(last_1 == a[i] or last_2 == a[i]) {
      cout << 0;
      exit(0);
    }
    return dfs(i+1, false, false, last_2, a[i]);
  }
  
  int res = 0;
  for(char j=a[i]+1; j<b[i]; j++){
    if(j == last_1 or j == last_2) continue;
    res += dfs(i+1, true, true, last_2, j);
  }
    
  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;
  cout << dfs(0, false, false, '%', '%');
}

signed main() {
  ios_base::sync_with_stdio(0);
  cin.tie(0);
  cout.tie(0);
  
  eight[0] = 1;
  for(int i=1; i<=19; i++) eight[i] = eight[i-1] * 8;
  
  solve();
}

• Subtask 1: 13.75 / 25
• Subtask 2: 60 / 75