504. Base 7

Given an integer, return its base 7 string representation.

Example 1:

Input: 100Output: "202"

Example 2:

Input: -7Output: "-10"

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

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public class Solution {    public String convertToBase7(int num) {        if (num == 0)return "0";StringBuilder re = new StringBuilder();boolean flag = false;if (num < 0) {flag = true;num = -num;}while (num != 0) {re.insert(0, num % 7);num /= 7;}if (flag)re.insert(0, '-');return re.toString();    }}