文章目录
一、题目
151. Reverse Words in a String
Given an input string s, reverse the order of the words.
A word is defined as a sequence of non-space characters. The words in s will be separated by at least one space.
Return a string of the words in reverse order concatenated by a single space.
Note that s may contain leading or trailing spaces or multiple spaces between two words. The returned string should only have a single space separating the words. Do not include any extra spaces.
Example 1:
Input: s = "the sky is blue"
Output: "blue is sky the"
Example 2:
Input: s = " hello world "
Output: "world hello"
Explanation: Your reversed string should not contain leading or trailing spaces.
Example 3:
Input: s = "a good example"
Output: "example good a"
Explanation: You need to reduce multiple spaces between two words to a single space in the reversed string.
Constraints:
1 <= s.length <= 104
s contains English letters (upper-case and lower-case), digits, and spaces ' '.
There is at least one word in s.
Follow-up: If the string data type is mutable in your language, can you solve it in-place with O(1) extra space?
二、题解
cpp
class Solution {
public:
string reverseWords(string s) {
vector<string> tmp;
istringstream ss(s);
string token;
while(getline(ss,token,' ')) tmp.push_back(token);
string res = "";
int n = tmp.size();
for(int i = n - 1;i >= 0;i--){
if(tmp[i] != ""){
res += tmp[i];
res += " ";
}
}
//去除末尾空格
while(res.back() == ' ') res.pop_back();
return res;
}
};