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  1. #include<bits/stdc++.h>
  2. using namespace std;
  3. class LastDigit
  4.     {
  5.     	int d = 0;
  6.     	long long int f(long long int x)
  7.             {
  8.  
  9.             	long long int sum = 0;
  10.             	while(x != 0)
  11.                     {
  12.                     	d++;
  13.                     	sum = sum + x;
  14.                     	//cout << sum << " ";
  15.                     	x =x/10;
  16.                     }
  17.             	return sum;
  18.             }
  19.     	public:
  20.     	long long findX(long long S)
  21.             {
  22.             	//return f(900000000000000000);
  23.             	long long int i;
  24.             	f(S);
  25.             	int dig = d;
  26.             	int d1 = dig -1;
  27.             	int ans = -1;
  28.             	double a1 = (double)(pow(10,d1) -1) / (9*pow(10,d1-1));
  29.             	d1++;
  30.             	double a2 = (double)(pow(10,d1) -1) / (9*pow(10,d1-1));
  31.             	a1 = 1/a1;
  32.             	a2 = 1/a2;
  33.             	a1 = S*a1;
  34.             	a2 = S*a2;
  35.             	for(i=a1 - 100 ; i <= a1 + 100 ; i++)
  36.                     if(f(i) - S == (long long )0)
  37.                     return i;
  38.                 for(i = a2 - 100 ;i <= a2 + 100 ; i++)
  39.                     if(f(i) - S == (long long )0)
  40.                     return i;
  41.                 return ans;
  42.  
  43.             }
  44.     };
  45.     int main()
  46.     {
  47.     	class LastDigit ld;
  48.     	cout << ld.findX(837592744927492746);
  49.     	return 0;
  50.     }
Success #stdin #stdout 0s 3468KB
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https://ideone.com/NjEMww
language:
C++14 (gcc 8.3)
created:
8 years ago
visibility:
secret

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