504. Base 7

题目来源【Leetcode】

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].

把十进制数变为7进制数，比较简单，直接放代码

class Solution {
public:
    string convertToBase7(int num) {
        string re;
        int temp = abs(num);
        if(num == 0) return "0";
        while(temp != 0){
            int t = temp%7;
            re += to_string(t);
            temp = temp/7;
        }
        reverse(re.begin(),re.end());
        if(num < 0) re = "-"+re;
        return re;
    }
};