一、题目

Given an integer num, return a string of its base 7 representation.

Example 1:

Input: num = 100
Output: “202”
Example 2:

Input: num = -7
Output: “-10”

Constraints:

-107 <= num <= 107

二、题解

class Solution {
public:string convertToBase7(int num) {if(num == 0) return "0";int flag = false;if(num < 0){num = -num;flag = true;}string res = "";while(num > 0){res += (num % 7 + '0');num /= 7;}reverse(res.begin(),res.end());if(flag) return "-" + res;else return res;}
};