LeetCode-Reverse Words in a String

文章目录

Problem:
Given an input string, reverse the string word by word.

For example,
Given s = “the sky is blue”,
return “blue is sky the”.

For C programmers: Try to solve it in-place in O(1) space.

public class Solution {
    public String reverseWords(String s) {
        String[] strs=s.trim().split("\\s+");
        StringBuilder sb=new StringBuilder();
        
        for(int i=strs.length-1;i>=0;i--)
        {
            sb.append(strs[i]);
            
            if(i!=0)
            {
                sb.append(" ");
            }
        }
        
        return sb.toString();
    }
}

thr runtime is 384ms

本来想说用二次字符串翻转来做的，比如第一次先以空格分隔翻转：eht yks si eulb，然后再一次进行全部翻转之后即可得到blue is sky the，但是代码提交到LeetCode之后他的Test Case中有去空格的Demo，老是Wrong，想想大致能用二次翻转完成就好，就没有继续调试了0-_-

public String reverseWords2(String s) {
	byte[] bs=s.getBytes();
    int length=bs.length;
    int start=0,end=0;
    
    for(int i=0;i<=length;i++)
    {
    	if(i==length || bs[i]==32)
    	{
    		end=i-1;
    		
    		reverse(bs,start,end);
        	start=i+1;
    	}
    }
    
    reverse(bs,0,length-1);
    
    return new String(bs);
}

private void reverse(byte[] bs,int i,int j){

	for(;i<j;i++,j--)
	{
		byte b=bs[i];
		bs[i]=bs[j];
		bs[j]=b;
	}
}

JUnit Test Code

List<TestExample> testExampleList=new ArrayList<TestExample>();
	
@Before
public void before(){

	this.testExampleList.add(new TestExample("   a   b ","b a"));//这个会失败 就没再测了
	this.testExampleList.add(new TestExample("LeetCode","LeetCode"));
	this.testExampleList.add(new TestExample("Hello World","World Hello"));
	this.testExampleList.add(new TestExample("the sky is blue","blue is sky the"));
	
}

@Test
public void test(){

	ReverseWordsinaString reverse=new ReverseWordsinaString();
	
	for(TestExample example:this.testExampleList)
	{
		Assert.assertEquals(reverse.reverseWords2(example.sourceStr),example.reverseStr);
	}
}

@After
public void after(){

	this.testExampleList.clear();
}

static class TestExample{
	public String sourceStr;
	public String reverseStr;
	
	public TestExample(String sourceStr,String reverseStr)	{
	
		this.sourceStr=sourceStr;
		this.reverseStr=reverseStr;
	}
}

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