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  1. #include <iostream>
  2. using namespace std;
  3.  
  4. // Returns the number of digits 3,6,9 that appear from 1 to x
  5. long long countClaps(long long x) {
  6.     if (x == 0) return 0;
  7.  
  8.     long long res = 0;
  9.     long long pow10 = 1;
  10.  
  11.     while (x / pow10 > 0) {
  12.         long long higher = x / (pow10 * 10);
  13.         int current = (x / pow10) % 10;
  14.         long long lower = x % pow10;
  15.  
  16.         // Counts the number of times is 3, 6, or 9 at the current position
  17.         for (int d : {3, 6, 9}) {
  18.             if (current > d) {
  19.                 res += (higher + 1) * pow10;
  20.             } else if (current == d) {
  21.                 res += higher * pow10 + lower + 1;
  22.             } else {
  23.                 res += higher * pow10;
  24.             }
  25.         }
  26.         pow10 *= 10;
  27.     }
  28.     return res;
  29. }
  30.  
  31. int main() {
  32.     long long a, b;
  33.     cin >> a >> b;
  34.  
  35.     // Count the number of times the digits 3, 6, 9 appear from a to b
  36.     cout << countClaps(b) - countClaps(a - 1) << endl;
  37.     return 0;
  38. }
Success #stdin #stdout 0s 5324KB
comments (?)
stdin
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999999 100000000
stdout
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238200006
https://ideone.com/tNqepf
language:
C++14 (gcc 8.3)
created:
10 hours ago
visibility:
public

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