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Leetcode 第151题 最新题解 Reverse Words in a String

2014年09月05日 ⁄ 综合 ⁄ 共 886字 ⁄ 字号 评论关闭

Reverse Words in a String

 Total Accepted: 67 Total
Submissions: 412
My Submissions

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.

Leetcode 很久没有更新题目了。太巧了,今天刚刚说150道题结贴,就出新题了,呵呵。

好吧,第一时间贴上来。

思路:

1 从后往前遍历string

2 保存单词,然后需要逆转,在保存到结果中

注意题目中的clarification,处理好其中的空格。

利用了两个额外string保存中间结果。空间复杂度为O(n).

时间复杂度是O(n),简单题目:2到3星级

	void reverseWords(string &s)
	{
		string rs;
		for (int i = s.length()-1; i >= 0; )
		{
			while (i >= 0 && s[i] == ' ') i--;
			if (i < 0) break;
			if (!rs.empty()) rs.push_back(' ');
			string t;
			while (i >= 0 && s[i] != ' ') t.push_back(s[i--]);
			reverse(t.begin(), t.end());
			rs.append(t);
		}
		s = rs;
	}

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