LeetCode #151 - Reverse Words in a String

最新推荐文章于 2018-12-02 22:41:31 发布

原创最新推荐文章于 2018-12-02 22:41:31 发布 · 204 阅读

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本文介绍了一种算法，用于将输入字符串中的单词顺序进行反转。通过整体翻转字符串再单独翻转每个单词来实现，有效处理了多余空格问题。

题目描述：

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.

解题方法就是把整个字符串翻转，然后再依次对每个单词翻转，对单词翻转可以利用两个指针实现，一个标记单词开头，一个标记单词末尾，同时要注意除去字符串首尾的空格。

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