[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:

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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:

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

Python:

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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:

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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:

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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++:

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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++:　　

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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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