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leetcode--Reverse Words in a String

2024-07-17 11:19:25   216人阅读

Problem Description:

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

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

click to show clarification.

Clarification:

  • What constitutes a word?
    A sequence of non-space characters constitutes a word.
  • Could the input string contain leading or trailing spaces?
    Yes. However, your reversed string should not contain leading or trailing spaces.
  • How about multiple spaces between two words?
    Reduce them to a single space in the reversed string.
分析：按照题目的意思，将字符串按照单词进行翻转，其实跟字符串循环移位的原理是一样的，先整体翻转一次，然后将其中每个单词再翻转一次即可达到目的，题目提到要注意将首尾多余的空格都去掉，同时中间单词之间只留下一个空格，多余的也去掉，编程时注意细节即可。具体代码如下：

class Solution {
public:

    void reverse1(string &s, int beg, int last)
    {
        if(beg==last)
            return;
        for(int i=beg,j=last;i<j;i++,j--)
        {
            char ch=s[i];
            s[i]=s[j];
            s[j]=ch;
        }
    }

    void reverseWords(string &s) {
        int i=0;
        while(i<s.size()&&s[i]==' ')
            i++;
        s.erase(0,i);//去掉开头的空格
        if(s.size()==0)
            return;
        int j=s.size()-1;
        while(j>=0&&s[j]==' ')
            j--;
        s.erase(j+1,s.size()-j);//去掉末尾的空格
        i=0;
        j=s.size();
        reverse1(s,0,j-1);//整体翻转一次
        
        int left=0,flag=0;
        while(s[i]!='\0')
        {

              if(s[i]==' ')
              {
                int k=i+1;
                while(s[k]==' ')
                {
                    flag++;
                    k++;
                }

                s.erase(i,flag);//去掉中间多余的空格

                reverse1(s,left,i-1);//每个单词依次翻转
                left=i+1;
                flag=0;
            }
            i++;
        }
        reverse1(s,left,i-1);
    }
};


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