<p>Given an input string <code>s</code>, reverse the order of the <strong>words</strong>.</p>

<p>A <strong>word</strong> is defined as a sequence of non-space characters. The <strong>words</strong> in <code>s</code> will be separated by at least one space.</p>

<p>Return <em>a string of the words in reverse order concatenated by a single space.</em></p>

<p><b>Note</b> that <code>s</code> 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.</p>

<p>&nbsp;</p>
<p><strong class="example">Example 1:</strong></p>

<pre>
<strong>Input:</strong> s = &quot;the sky is blue&quot;
<strong>Output:</strong> &quot;blue is sky the&quot;
</pre>

<p><strong class="example">Example 2:</strong></p>

<pre>
<strong>Input:</strong> s = &quot;  hello world  &quot;
<strong>Output:</strong> &quot;world hello&quot;
<strong>Explanation:</strong> Your reversed string should not contain leading or trailing spaces.
</pre>

<p><strong class="example">Example 3:</strong></p>

<pre>
<strong>Input:</strong> s = &quot;a good   example&quot;
<strong>Output:</strong> &quot;example good a&quot;
<strong>Explanation:</strong> You need to reduce multiple spaces between two words to a single space in the reversed string.
</pre>

<p>&nbsp;</p>
<p><strong>Constraints:</strong></p>

<ul>
	<li><code>1 &lt;= s.length &lt;= 10<sup>4</sup></code></li>
	<li><code>s</code> contains English letters (upper-case and lower-case), digits, and spaces <code>&#39; &#39;</code>.</li>
	<li>There is <strong>at least one</strong> word in <code>s</code>.</li>
</ul>

<p>&nbsp;</p>
<p><b data-stringify-type="bold">Follow-up:&nbsp;</b>If the string data type is mutable in your language, can&nbsp;you solve it&nbsp;<b data-stringify-type="bold">in-place</b>&nbsp;with&nbsp;<code data-stringify-type="code">O(1)</code>&nbsp;extra space?</p>

#include<cstring>
class Solution {
public:
    string reverseWords(string s) {
        string ans="";
        char ch[s.size()+1];
        strcpy(ch,s.c_str());
        char *p=strtok(ch," ");
        stack<string> st;
        while(p!=NULL)
        {
            st.push(p);
            p=strtok(NULL," ");
        }
        while(!st.empty())
        {
            ans=ans+st.top();
            st.pop();
            if(!st.empty()) ans=ans+" ";
        }
        return ans;
        // // stack<string> s1;
        // // stringstream s2(s);
        // // string word;
        // // string ans;ans="";
        // // while( s2>>word) s1.push(word);
        // // while(!s1.empty())
        // // {
        // //     ans=ans+s1.top();
        // //     s1.pop();
        // //     if(!s1.empty())
        // //     {
        // //         ans=ans+" ";
        // //     }
        // // }
        // // return ans;
        // int n=s.size();
        // char c[n+1];
        // strcpy(c,s.c_str());
        // char *p=strtok(c," ");
        // stack<string> st;
        // while(p!=NULL)
        // {
        //     st.push(p);
        //     p=strtok(NULL," ");
        // }
        // string ans="";
        // while(!st.empty())
        // {
        //     ans=ans+st.top();
        //     st.pop();
        //     if(!st.empty())
        //     {
        //         ans=ans+" ";
        //     }
        // }
        // return ans;
    }
};
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