<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>

class Solution {
public:

    string reverseUtil(int i, int j, string s){
        // cout<<i<<" "<<j<<" "<<s<<"\n";
        while(i < j){
            char c = s[i];
            s[i] = s[j];
            s[j] = c;
            i++;
            j--;
        }
        // cout<<s<<"\n";
        return s;
    }
    string reverseWords(string s) {
        int i = 0;
        while(s[i] == ' '){
            i++;
        }
        s = s.substr(i);

        s = s + ' '; // adding a trailing space

        int itr = 0;
        int prev = 0;
        bool w = false;
        int b = 0;
        while(itr < s.size()){
            if(s[itr] != ' '){
                w = true;
                itr++;
                continue;
            }
            if(s[itr] == ' ' && w)
            {
                //reverse logic
                s = reverseUtil(prev, itr-1, s);
                w = false;
                prev = itr - b + 1;
                // b = 0;
            } else if(s[itr] == ' '){
                b++;
                // cout<<"zero "<<b<<"\n";
            }
            itr++;
        }

        i = s.size()-1;
        while(s[i] == ' ')
        {    
            i--;
        }
        
        s = s.substr(0, i+1);

        // cout<<s<<"\n";
        return reverseUtil(0, s.size()-1, s);
    }
};
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