504.七进制数.js

/*
 * @lc app=leetcode.cn id=504 lang=javascript
 *
 * [504] 七进制数
 *
 * https://leetcode-cn.com/problems/base-7/description/
 *
 * algorithms
 * Easy (46.36%)
 * Likes:    22
 * Dislikes: 0
 * Total Accepted:    5.6K
 * Total Submissions: 12K
 * Testcase Example:  '100'
 *
 * 给定一个整数，将其转化为7进制，并以字符串形式输出。
 *
 * 示例 1:
 *
 *
 * 输入: 100
 * 输出: "202"
 *
 *
 * 示例 2:
 *
 *
 * 输入: -7
 * 输出: "-10"
 *
 *
 * 注意: 输入范围是 [-1e7, 1e7] 。
 *
 */
/**
 * 短除法
 * @param {number} num
 * @return {string}
 */
var convertToBase7 = function(num) {
  if (num === 0) return "0";
  let res = "";
  const flag = num < 0 ? "-" : "";
  num < 0 && (num = -num);
  while (num) {
    res = (num % 7) + res;
    num = Math.floor(num / 7);
  }
  return flag + res;
};