504. Base 7

• Difficulty: Easy

• Topics:

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Problem:

Given an integer, return its base 7 string representation.

Example 1:

Input: 100
Output: "202"

Example 2:

Input: -7
Output: "-10"

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

Solutions:

class Solution {
public:
    string convertToBase7(int num) {
        if (num == 0)   return "0";
        int sign = 1;
        if (num < 0) {
            sign = -1;
            num = -num;
        }

        string ret;
        while (num > 0) {
            ret.push_back('0' + num % 7);
            num /= 7;
        }

        if (sign == -1) {
            ret.push_back('-');
        }

        reverse(ret.begin(), ret.end());
        return ret;
    }
};