Leetcode 151. Reverse Words in a String

class Solution
{
public:
void reverseWords(string &s)
{
string ans;
ans.clear();
for (int i = 0;i != s.size() / 2;i++)
swap(s[i], s[s.size() - i - 1]);
string tmp;

for (int i = 0;i < s.size();i++)
{
if (s[i] != ' ')
tmp.push_back(s[i]);

else if (tmp.size() != 0)
{
for (int j = 0;j != tmp.size() / 2;j++)
swap(tmp[j], tmp[tmp.size() - j - 1]);
if (ans.size() != 0)
ans.append(" ");
ans += tmp;
tmp.clear();
}
}

if (tmp.size() != 0)
{
if (ans.size() != 0)
ans.append(" ");
for (int j = 0;j != tmp.size() / 2;j++)
swap(tmp[j], tmp[tmp.size() - j - 1]);
ans += tmp;
}
s.clear();
s = ans;
}
};