[LeetCode] Reverse Words in a String-优快云博客

本文介绍了一种用于将输入字符串中的单词进行反转的算法，并提供了两种不同的实现方式：一种使用了stringstream和堆栈；另一种通过遍历字符串并逐个处理单词来实现。这两种方法都能有效地去除多余的空格并确保单词之间的单个空格间隔。

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

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

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.

class Solution {
public:
    void reverseWords(string &s) {
        stringstream str(s);
        string word, res;
        stack<string> stk;
        while(str >> word)
            stk.push(word);
        if(!stk.empty())
        {
            res = stk.top();
            stk.pop();
        }
        while(!stk.empty())
        {
            res += " ";
            res += stk.top();
            stk.pop();
        }
        s = res;
    }
};

上面是我自己的方法，用了stringstream这个流，头文件是<sstream>，搜了下别人的方法，也非常巧妙。

class Solution {
public:
    void reverseWords(string &s) {
        string res;
        for(int i = s.length() - 1; i >= 0; i--)
        {
            while(i >= 0 && s[i] == ' ') i--;
            if(i < 0)   break;
            if(!res.empty())
                res += " ";
            string t;
            while(i >= 0 && s[i] != ' ')
                t += s[i--];
            reverse(t.begin(), t.end());
            res += t;
        }
        s = res;
    }
};