LeetCode-Reverse Words in a String

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于 2014-07-28 11:02:49 发布

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分类专栏： Stack Reserve Cracking LeetCode String Trick 文章标签： leetcode Reverse Words in a S

本文链接：https://blog.youkuaiyun.com/HolyDominat/article/details/38226313

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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实现。通过使用栈来存储每个单词，并最终将它们按正确顺序重新组合成一个字符串。讨论了如何处理输入字符串中的空白字符、多个连续空格以及单词边界等问题。

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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.

Solution:

Code:

class Solution {
public:
    void reverseWords(string &s) {
        int length = s.size();
        stack<string> stk;
        int start;
        bool word = false;
        for (int i = 0; i < length; ++i)
            if (s[i] == ' ' && word) {
                stk.push(s.substr(start, i-start));
                word = false;
            } else if (s[i] != ' ' && !word) {
                word = true;
                start = i;
            }
        //attention
        if (word) stk.push(s.substr(start, length-start));
        if (stk.empty()) {
            s = "";
            return;
        } else {
            s = stk.top();
            stk.pop();
            while (!stk.empty()) {
                s += ' ' + stk.top();
                stk.pop();
            }
            return;
        }
    }
};