LeetCode: Reverse Words in a String [151]

【题目】

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.

【题意】

给定一个字符串，按单词反转

【思路】

现切分字符串，然后反向拼接

【代码】

class Solution {
public:

void reverseWords(string &s) {
stack<string> words;
int start = -1;	//记录单词开始的位置
for(int i=0; i<s.length(); i++){
if(s[i]==' '){
if(i!=0 && s[i-1]!=' '){
//一个单词结束
words.push(s.substr(start, i-start));
start = -1;
}
}
else{
if(i==0 || s[i-1]==' '){
start = i;
}
}
}
if(start!=-1)words.push(s.substr(start, s.length()-start));

//拼接成反向单词
s = "";
int count=0;
while(!words.empty()){
count++;
if(count==1)s+=words.top();
else s+=" "+words.top();
words.pop();
}
}
};