[LintCode] Reverse Words in a String 翻转字符串中的单词

Given an input string, reverse the string word by word.

For example,
Given s = "

the sky is blue

",
return "

blue is sky the

".

Have you met this question in a real interview?

Yes

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上的原题，请参见我之前的博客Reverse Words in a String。

解法一：

class Solution {
public:
/**
* @param s : A string
* @return : A string
*/
string reverseWords(string s) {
int storeIndex = 0, n = s.size();
reverse(s.begin(), s.end());
for (int i = 0; i < n; ++i) {
if (s[i] != ' ') {
if (storeIndex != 0) s[storeIndex++] = ' ';
int j = i;
while (j < n && s[j] != ' ') s[storeIndex++] = s[j++];
reverse(s.begin() + storeIndex - (j - i), s.begin() + storeIndex);
i = j;
}
}
return string(s.begin(), s.begin() + storeIndex);
}
};

解法二：

class Solution {
public:
/**
* @param s : A string
* @return : A string
*/
string reverseWords(string s) {
string res = "", t = "";
istringstream is(s);
while (getline(is, t, ' ')) {
if (t.empty()) continue;
res = (res.empty() ? t : (t + " " + res));
}
return res;
}
};

解法三：

class Solution {
public:
/**
* @param s : A string
* @return : A string
*/
string reverseWords(string s) {
istringstream is(s);
is >> s;
string t;
while (is >> t) {
s = t + " " + s;
}
return (s[0] == ' ') ? "" : s;
}
};