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Formatted question description: https://leetcode.ca/all/504.html

504. Base 7

Level

Easy

Description

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].

Solution

If nums is 0, simply return “0”.

Otherwise, split the sign out and deal with the absolute value of num. Each time divide num by 7 and store the remainders in the reverse order until num becomes 0. If num is negative initially, add the negative sign. Finally return the string of base 7 representation.

• Java
• C++
• Python
• Go
• TypeScript
• RenderScript

• class Solution {
      public String convertToBase7(int num) {
          if (num == 0)
              return "0";
          int sign = num >= 0 ? 1 : -1;
          num = Math.abs(num);
          StringBuffer base7 = new StringBuffer();
          while (num > 0) {
              int remainder = num % 7;
              base7.insert(0, (char) (remainder + '0'));
              num /= 7;
          }
          if (sign < 0)
              base7.insert(0, '-');
          return base7.toString();
      }
  }
  

• // OJ: https://leetcode.com/problems/base-7/
  // Time: O(logN)
  // Space: O(logN)
  class Solution {
  public:
      string convertToBase7(int n) {
          if (n == 0) return "0";
          string ans;
          bool neg = false;
          if (n < 0) n = -n, neg = true;
          while (n) {
              ans += '0' + n % 7;
              n /= 7;
          }
          if (neg) ans += '-';
          reverse(begin(ans), end(ans));
          return ans;
      }
  };
  

• class Solution:
      def convertToBase7(self, num: int) -> str:
          if num == 0:
              return '0'
          if num < 0:
              return '-' + self.convertToBase7(-num)
          ans = []
          while num:
              ans.append(str(num % 7))
              num //= 7
          return ''.join(ans[::-1])
  
  ############
  
  class Solution(object):
    def convertToBase7(self, num):
      """
      :type num: int
      :rtype: str
      """
  
      def convertHelper(num, base):
        sign = ""
        if num < 0:
          sign = "-"
        num = abs(num)
        ans = 0
        unit = 1
        while num:
          ans += (num % base) * unit
          num /= base
          unit *= 10
        return sign + str(ans)
  
      return convertHelper(num, 7)
  
  

• func convertToBase7(num int) string {
  	if num == 0 {
  		return "0"
  	}
  	if num < 0 {
  		return "-" + convertToBase7(-num)
  	}
  	ans := []byte{}
  	for num != 0 {
  		ans = append([]byte{'0' + byte(num%7)}, ans...)
  		num /= 7
  	}
  	return string(ans)
  }
  

• function convertToBase7(num: number): string {
      if (num == 0) {
          return '0';
      }
      let res = '';
      const isMinus = num < 0;
      if (isMinus) {
          num = -num;
      }
      while (num != 0) {
          const r = num % 7;
          res = r + res;
          num = (num - r) / 7;
      }
      return isMinus ? '-' + res : res;
  }
  
  

• impl Solution {
      pub fn convert_to_base7(mut num: i32) -> String {
          if num == 0 {
              return String::from("0");
          }
          let mut res = String::new();
          let is_minus = num < 0;
          if is_minus {
              num = -num;
          }
          while num != 0 {
              res.push_str((num % 7).to_string().as_str());
              num /= 7;
          }
          if is_minus {
              res.push('-');
          }
          res.chars().rev().collect()
      }
  }
  
  

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