Welcome to Subscribe On Youtube

Formatted question description: https://leetcode.ca/all/1256.html

1256. Encode Number

Level

Medium

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:

Image text

Example 1:

Input: num = 23

Output: “1000”

Example 2:

Input: num = 107

Output: “101100”

Constraints:

  • 0 <= num <= 10^9

Solution

If n is 0, then f(n) is "". If 1 <= n < 3, then f(n) is a binary string with length 1. If 3 <= n < 7, then f(n) is a binary string with length 2. If 7 <= n < 15, then `f(n) is a binary string with length 3.

The encoding function is as follows. For the given number num, obtain the number of bits bits for number num + 1, where the number of bits means the number of bits remaining after removing leading zeros, calculate difference as the difference between num + 1 and 2 ^ bits, and return the binary representation of difference.

  • class Solution {
    public String encode(int num) {
        num++;
        int bits = (int) (Math.log(num) / Math.log(2));
        int difference = num - (int) Math.pow(2, bits);
        String encodeStr = binary(difference, bits);
        return encodeStr;
    }

    public String binary(int num, int bits) {
        String str = "";
        for (int i = 0; i < bits; i++) {
            int remainder = num % 2;
            str = remainder + str;
            num /= 2;
        }
        return str;
    }
}

  • // OJ: https://leetcode.com/problems/encode-number/
// Time: O(logN)
// Space: O(logN)
class Solution {
public:
    string encode(int n) {
        ++n;
        string ans;
        int len = log(n);
        while (n) {
            ans += '0' + (n & 1);
            n >>= 1;
        }
        if (ans.size() > len) ans.pop_back();
        return string(rbegin(ans), rend(ans));
    }
};

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


  • 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);
}

All Problems

All Solutions