[LeetCode] 504. Base 7 基数七

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].

给一个整数，返回它的七进制数。

解法1: 迭代

解法2: 递归

Java:

public class Solution {
    public String convertTo7(int num) {
        if (num == 0) return "0";
        
        StringBuilder sb = new StringBuilder();
        boolean negative = false;
        
        if (num < 0) {
            negative = true;
        }
        while (num != 0) {
            sb.append(Math.abs(num % 7));
            num = num / 7;
        }
        
        if (negative) {
            sb.append("-");
        }
        
        return sb.reverse().toString();
    }
}　

Java:

public String convertTo7(int num) {
    if (num < 0)
        return '-' + convertTo7(-num);
    if (num < 7)
        return num + "";
    return convertTo7(num / 7) + num % 7;
}　　

Python:

class Solution(object):
    def convertToBase7(self, num):
        """
        :type num: int
        :rtype: str
        """
        if num == 0:
            return '0'
        if num < 0:
            return '-' + self.convertToBase7(-num)
        
        res = ''
        while num > 0:
            res = str(num % 7) + res
            num = num / 7
            
        return res  

Python:

def convertTo7(self, num):
    if num == 0: return '0'
    n, res = abs(num), ''
    while n:
      res = str(n % 7) + res
      n //= 7
    return res if num > 0 else '-' + res　　

Python:

def convertTo7(self, num):
    if num < 0: return '-' + self.convertTo7(-num)
    if num < 7: return str(num)
    return self.convertTo7(num // 7) + str(num % 7)　　

C++:

class Solution {
public:
    string convertToBase7(int num) {
        if (num == 0) return "0";
        string res = "";
        bool positive = num > 0;
        while (num != 0) {
            res = to_string(abs(num % 7)) + res;
            num /= 7;
        }
        return positive ? res : "-" + res;
    }
};

C++:　　

class Solution {
public:
    string convertToBase7(int num) {
        if (num < 0) return "-" + convertToBase7(-num);
        if (num < 7) return to_string(num);
        return convertToBase7(num / 7) + to_string(num % 7);
    }
};

　　

　　

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