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  1. #include <bits/stdc++.h>
  2. using namespace std;
  3.  
  4. // check if integer a has digit '7' in its decimal form
  5. bool has7(long long a) {
  6.     while (a > 0) {
  7.         if ((a % 10) == 7) return true;
  8.         a /= 10;
  9.     }
  10.     return false;
  11. }
  12.  
  13. int solve_one(long long n) {
  14.     // List of all-9 numbers up to 10 digits
  15.     static long long all9[10] = {
  16.         9LL,
  17.         99LL,
  18.         999LL,
  19.         9999LL,
  20.         99999LL,
  21.         999999LL,
  22.         9999999LL,
  23.         99999999LL,
  24.         999999999LL,
  25.         9999999999LL
  26.     };
  27.  
  28.     int best = INT_MAX;
  29.     for (int i = 0; i < 10; i++) {
  30.         long long x = all9[i];
  31.         long long cur = n;
  32.         int steps = 0;
  33.         // keep adding x until we see a '7'
  34.         while (!has7(cur)) {
  35.             cur += x;
  36.             steps++;
  37.             // (In practice, steps will be ≤ 10–12 here, because each digit
  38.             //  cycles mod 10.)
  39.         }
  40.         best = min(best, steps);
  41.     }
  42.     return best;
  43. }
  44.  
  45. int main() {
  46.     ios::sync_with_stdio(false);
  47.     cin.tie(nullptr);
  48.  
  49.     int T;
  50.     cin >> T;
  51.     while (T--) {
  52.         long long n;
  53.         cin >> n;
  54.         // If n already has a '7', 0 moves are needed
  55.         if (has7(n)) {
  56.             cout << 0 << "\n";
  57.         } else {
  58.             cout << solve_one(n) << "\n";
  59.         }
  60.     }
  61.     return 0;
  62. }
  63.  
Success #stdin #stdout 0.01s 5280KB
comments (?)
stdin
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16
51
60
61
777
12345689
1000000000
2002
3001
977
989898986
80
800001
96
70
15
90
stdout
copy 
3
2
1
0
1
3
5
4
0
7
1
2
7
0
7
3
https://ideone.com/TD7NzK
language:
C++ (gcc 8.3)
created:
19 hours ago
visibility:
public

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