151. Reverse Words in a String

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

Example:

Input: "the sky is blue",
Output: "blue is sky the".

Note:

• A word is defined as a sequence of non-space characters.
• Input string may contain leading or trailing spaces. However, your reversed string should not contain leading or trailing spaces.
• You need to reduce multiple spaces between two words to a single space in the reversed string.

Follow up: For C programmers, try to solve it in-place in O(1) space.

思路

这个是老题目了，字符串倒序，最简单的方法是先字符串整体翻转一次，然后每个单词再翻转一次即可。

这里不想用这种方法，迷上了使用istringstream来处理这种string类型的题目。

• 以空格' '为分隔符进行分割
• 如果有多个空格连在一起，那么分隔到的字符串为空，跳过即可
• 将分割后的字符串倒序串接即可

代码

class Solution {
public:
    void reverseWords(string &s) {
        istringstream iss(s);
        string tmp = "";
        s = "";
        while (getline(iss, tmp, ' ')) {
            if (tmp.empty()) continue;
            s = s.empty() ? tmp : (tmp + " " + s);
        }
    }
};