Reverse Words in a String
Total Accepted: 67 Total
Submissions: 412My Submissions
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.
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; }