Given a string, you need to reverse the character order of each word in the string while still preserving the initial order of spaces and words.

Example 1:

Input: "Let's take LeetCode contest"
Output: "s'teL ekat edoCteeL tsetnoc"

Note: in a string, each word is separated by a single space, and there are no extra spaces in the string.

I'm tired of this problem. I started to exceed the memory space limit

Failed solution and code: just stack each word, and then stack it once

class Solution {
public:
    string reverseWords(string s) {
        stack<char> tmp;
        string result;
        int i = 0;
        for(string::iterator iter = s.begin(); iter != s.end();iter++)
        {
            if(*iter != ' ')
            {
                tmp.push(*iter);
            }
            if(*iter == ' '||  *(iter + 1) == NULL)
            {
                while(!tmp.empty())
                {
                    result = result + tmp.top();
                    tmp.pop();
                }
                if(*(iter + 1))
                    result = result + ' ';
            }
        }
        return result;
    }
};

The final solution is as follows:

class Solution {
public:
    string reverseWords(string s) {
        vector<int> a;
        if(s.empty())
            return s;
        int i = 0;
        for(auto c:s)
        {
            if(c == ' ')
                a.push_back(i);
            i++;
        }
        int size = a.size();
        if(size == 0)
        {
            reverse(s.begin(),s.end());
            return s;
        }
        reverse(s.begin(),s.begin()+a[0]);
        for(int j = 0;j < size - 1;j++)
        {
            //cout << *(s.begin() + a[j]);
            reverse(s.begin() + a[j] + 1, s.begin() + a[j + 1]);
        }
        reverse(s.begin()+a[size-1]+1,s.end());
        return s;
    }
};