Question

1256. Encode Number

中文文档

Description

Given a non-negative integer num, Return its _encoding_ string.

The encoding is done by converting the integer to a string using a secret function that you should deduce from the following table:

 

Example 1:

Input: num = 23

Output: "1000"

Example 2:

Input: num = 107

Output: "101100"

 

Constraints:

• 0 <= num <= 10^9

Solutions

Solution 1: Bit Manipulation

We add one to $num$, then convert it to a binary string and remove the highest bit $1$.

The time complexity is $O(\log n)$, and the space complexity is $O(\log n)$. Where $n$ is the size of $num$.

class Solution:
  def encode(self, num: int) -> str:
    return bin(num + 1)[3:]

class Solution {
  public String encode(int num) {
    return Integer.toBinaryString(num + 1).substring(1);
  }
}

class Solution {
public:
  string encode(int num) {
    bitset<32> bs(++num);
    string ans = bs.to_string();
    int i = 0;
    while (ans[i] == '0') {
      ++i;
    }
    return ans.substr(i + 1);
  }
};

func encode(num int) string {
  num++
  s := strconv.FormatInt(int64(num), 2)
  return s[1:]
}

function encode(num: number): string {
  ++num;
  let s = num.toString(2);
  return s.slice(1);
}