LeetCode - Easy - 504. Base 7

红太狼 2022-10-16 04:59 7阅读 0赞

## Topic ##

*  Math

## Description ##

[https://leetcode.com/problems/base-7/][https_leetcode.com_problems_base-7]

Given an integer num, return a string of its base 7 representation.

**Example 1:**

Input: num = 100
    Output: "202"

**Example 2:**

Input: num = -7
    Output: "-10"

**Constraints:**

*   − 1 0 7 < = n u m < = 1 0 7 -10^7 <= num <= 10^7 −107<=num<=107

## Analysis ##

方法一：迭代法

方法二：使用库方法

方法三：递归法

## Submission ##

public class Base7 { 
    	
    	//方法一：迭代法
        public String convertToBase7(int num) { 
        	StringBuilder sb = new StringBuilder();
        	boolean negative = num < 0;
        	num = Math.abs(num);
        	do { 
        		int shang = num / 7;
        		int yu = num - shang * 7;
        		sb.append(yu);
        		num = shang;
        	}while(num > 0);
        	
        	if(negative)
        		sb.append('-');
        	
        	return sb.reverse().toString();
        }
        
        //方法二：使用库方法
        public String convertToBase7_2(int num) { 
        	return Integer.toString(num, 7);
        }
        
        //方法三：递归法
        public String convertToBase7_3(int n) { 
            if (n < 0) return "-" + convertToBase7_3(-n);
            if (n < 7) return Integer.toString(n);
            return convertToBase7_3(n / 7) + Integer.toString(n % 7);
        }
    }

## Test ##

import static org.junit.Assert.*;
    import org.junit.Test;
    
    public class Base7Test { 
    
    	@Test
    	public void test() { 
    		Base7 obj = new Base7();
    
    		assertEquals("0", obj.convertToBase7(0));
    		assertEquals("202", obj.convertToBase7(100));
    		assertEquals("-10", obj.convertToBase7(-7));
    		assertEquals("-11", obj.convertToBase7(-8));
    		
    		assertEquals("0", obj.convertToBase7_2(0));
    		assertEquals("202", obj.convertToBase7_2(100));
    		assertEquals("-10", obj.convertToBase7_2(-7));
    		assertEquals("-11", obj.convertToBase7_2(-8));
    		
    		assertEquals("0", obj.convertToBase7_3(0));
    		assertEquals("202", obj.convertToBase7_3(100));
    		assertEquals("-10", obj.convertToBase7_3(-7));
    		assertEquals("-11", obj.convertToBase7_3(-8));
    	}
    }

[https_leetcode.com_problems_base-7]: https://leetcode.com/problems/base-7/