Easy+ Ā· base conversion
Decimal to Binary
Convert a decimal number to binary with nothing but % 2 and / 2. The single most common interview warm-up after Fibonacci.
Problem
Input: one integer n (0 ā¤ n ā¤ 10ā¹).
Output: the binary representation of n, with no leading zeros (0 prints as 0).
Sample:
| Input | Output |
|---|---|
5 | 101 |
255 | 11111111 |
Your solution
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Stuck? Hints
Hint 1 ā the two operations
n % 2 is the LAST bit; n / 2 drops it. Either collect the bits and reverse them, or prepend each new bit to a string.
Hint 2 ā the zero trap
The loop while (n > 0) never runs for n = 0, so you would print nothing. Handle 0 first (it prints as 0).
Solution (try first!)
int n = int.Parse(Console.ReadLine());
if (n == 0) { Console.WriteLine("0"); return; }
string bits = "";
while (n > 0) { bits = (n % 2) + bits; n = n / 2; }
Console.WriteLine(bits);Prepending to a string is O(nĀ²) for huge inputs ā the string vs StringBuilder article explains when that matters. Next: Count the Primes.