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  1. #include <iostream>
  2. #include <string>
  3.  
  4. bool isClap(int digit) {
  5.     return digit == 3 || digit == 6 || digit == 9;
  6. }
  7.  
  8. // Input validation
  9. bool checkInput(long long& a, long long& b) {
  10.     // Read two integers from input
  11.     if (!(std::cin >> a >> b)) 
  12.     	return false;
  13.  
  14.     std::cin >> std::ws;
  15.     char c;
  16.     // Check for extra characters (must be newline)
  17.     if (std::cin.get(c) && c != '\n') 
  18.     	return false;
  19.  
  20.    return (a >= 1 && b <= 100000000 && a <= b);
  21. }
  22.  
  23. // Count occurrences of 3, 6, 9 in numbers from 1 to n
  24. long long countClaps(long long n) {
  25.     std::string S = std::to_string(n);
  26.     int lengthOfNumber = S.size();
  27.     long long count = 0;
  28.     long long right_multiplier = 1;
  29.  
  30.     for (int pos = lengthOfNumber - 1; pos >= 0; --pos) {
  31.         int currentNumber = S[pos] - '0';
  32.  
  33.         // Get number formed by digits to the left of current position
  34.         long long leftValue = (pos == 0) ? 0 : std::stoll(S.substr(0, pos));
  35.         // Get number formed by digits to the right of current position
  36.         long long rightValue = (pos == lengthOfNumber - 1) ? 0 : std::stoll(S.substr(pos + 1));
  37.  
  38.         count += leftValue * right_multiplier * 3;
  39.  
  40.         for (int d = 0; d < currentNumber; ++d) {
  41.             if (isClap(d))
  42.                 count += right_multiplier;
  43.         }
  44.  
  45.         if (isClap(currentNumber))
  46.             count += rightValue + 1;
  47.  
  48.         right_multiplier *= 10;
  49.     }
  50.  
  51.     return count;
  52. }
  53. // Calculate claps from a to b
  54. long long solve(long long a, long long b) {
  55.     return countClaps(b) - countClaps(a - 1);
  56. }
  57.  
  58. int main() {
  59.     long long a, b;
  60.     if (!checkInput(a, b)) {
  61.         std::cout << "Invalid input! Please enter two integers a and b (1 <= a <= b <= 100000000) separated by a space." << std::endl;
  62.         return 1;
  63.     }
  64.     std::cout << solve(a, b) << std::endl;
  65.     return 0;
  66. }
Success #stdin #stdout 0.01s 5288KB
comments (?)
stdin
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999999 10000000
stdout
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19200006
https://ideone.com/KEJi3k
language:
C++14 (gcc 8.3)
created:
7 days ago
visibility:
public

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