LeetCode 151. Reverse Words in a String

题目描述:

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

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

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.

翻转一个字符串中的单词, 先翻转整个字符串然后再把每一个单词都翻转一次即可. 但是要考虑输入字符串前后的空格和单词间多余空格.

class Solution {
public:
    void reverseWords(string &s) {
        trimString(s);
        reverse(s.begin(), s.end());
        for(int i = 0; i < s.size(); i++){
            int j;
            for(j = i + 1; j < s.size() && s[j] != ' '; j++);
            reverse(s.begin() + i, s.begin() + j);
            if(j == s.size()){
                break;
            }
            else{
                while(j + 1 < s.size() && s[j + 1] == ' ') s.erase(j + 1, 1);
                i = j;
            }
        }
    }
    
    void trimString(string &s){
        while(s.front() == ' ') s.erase(s.begin());
        while(s.back() == ' ') s.pop_back();
    }
};