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  1. #include <bits/stdc++.h>
  2. using namespace std;
  3. long long lowerBound,actualAge;
  4. long long powah(long long a,long long b){
  5.     long long ans = 1;
  6.     for(int i=1;i<=b;i++)
  7.         ans = ans * a;
  8.     return ans;
  9. }
  10. long long convert(long long base){
  11.     if(actualAge < base)
  12.         return actualAge;
  13.     vector<int> d;
  14.     long long cpy = actualAge, ans=0;
  15.     while(cpy > 0){
  16.         long long t = cpy % base;
  17.         if(t > 9)
  18.             return -1;
  19.         d.push_back(t);
  20.         cpy = cpy / base;
  21.     }
  22.     for(int i=d.size()-1;i>=0;i--){
  23.         ans = ans * 10 + d[i];
  24.     }
  25.     return ans;
  26. }
  27.  
  28. long long conv(long long base, long long num){
  29.     long long ans = 0;
  30.     long long exp = 1;
  31.     while(num){
  32.         int last = num%10;
  33.         ans+=last*exp;
  34.         num/=10;
  35.         exp*=base;
  36.     }
  37.     return ans;
  38. }
  39.  
  40. int main() {
  41.  
  42.     cin>>actualAge>>lowerBound;
  43.     long long ans = -1;
  44.     long long ansAge = 5000000000000000000;
  45.     for(long long curAge = lowerBound; curAge<=9999LL; curAge++){
  46.         long long lowBase = 10;
  47.         long long num_digits;
  48. 	if(curAge > 999)
  49. 		num_digits = 3;
  50. 	else if(curAge > 99)
  51. 		num_digits = 2;
  52. 	else if(curAge > 9)
  53. 		num_digits = 1;
  54. 	else
  55. 		num_digits = 0;
  56. 	long long high_base_order = 1;
  57. 	if(num_digits!=0)
  58. 		high_base_order = 18/num_digits;
  59. 	long long highBase = powah(10,high_base_order);
  60.         while(lowBase<=highBase){
  61.             long long midBase = (lowBase+highBase)/2;
  62.             long long num = conv(midBase, curAge);
  63.             if(num<0)	highBase = midBase-1;
  64.             if(num>actualAge)   highBase = midBase-1;
  65.             if(num<actualAge)   lowBase = midBase+1;
  66.             if(num==actualAge){
  67.                 if(ansAge>curAge){
  68.                     ansAge=curAge;
  69.                     ans = midBase;
  70.                 }
  71.                 break;
  72.             }
  73.         }
  74.     }
  75.     for(long long base = 10; base<=100000; base++){
  76.         long long num = convert(base);
  77.         if(num>=lowerBound){
  78.             if(ansAge>num){
  79.                 ansAge=num;
  80.                 ans = base;
  81.             }
  82.         }
  83.     }
  84.     cout<<ans;
  85.     return 0;
  86. }
Success #stdin #stdout 0.04s 3464KB
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https://ideone.com/g4BjJD
language:
C++14 (gcc 8.3)
created:
8 years ago
visibility:
public

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