Base 7

• LeetCode: Base 7

• Problem:

Given an integer, return its base 7 string representation.

• Note:

The input will be in range of [-1e7, 1e7].

• Examples:

Input: 100
Output: "202"

Input: -7
Output: "-10"

• Analysis:

Use module and divide 7 to get base 7 string.

• Code - Java:

class Solution {
    public String convertToBase7(int num) {
        if (num == 0) {
            return "0";
        }
        boolean neg = num < 0 ? true : false;
        num = Math.abs(num);
        StringBuilder builder = new StringBuilder();
        while (num > 0) {
            builder.append(String.valueOf(num % 7));
            num /= 7;
        }
        return neg ? "-" + builder.reverse().toString() : builder.reverse().toString();
    }
}

• Code - C++:

class Solution {
public:
    string convertToBase7(int num) {
        if (num == 0) {
            return "0";
        }
        bool neg = num < 0 ? true : false;
        num = abs(num);
        string builder = "";
        while (num > 0) {
            builder += to_string(num % 7);
            num /= 7;
        }
        reverse(builder.begin(), builder.end());
        return neg ? "-" + builder : builder;
    }
};

• Code - Python:

class Solution(object):
    def convertToBase7(self, num):
        """
        :type num: int
        :rtype: str
        """
        if num == 0:
            return str(0)
        neg = False
        if num < 0:
            neg = True
            num = abs(num)
        builder =  ""
        while num > 0:
            builder += str(num % 7)
            num /= 7
        if neg:
            return "-" + builder[::-1]
        return builder[::-1]