class Count2 { public: int countNumberOf2s(int n) { // write code here int low = 0; int high = n / 10; int cur = n % 10; int digit = 1; int count = 0; while (high || cur) { if (cur < 2) { count += high * digit; } else if (cur == 2) { count += high * digit + 1 + low; } else { count += (high + 1) * digit; } low +=cur*digit; cur = high%10; high /=10; digit *=10; } return count; } };