<p>Given a string <code>paragraph</code> and a string array of the banned words <code>banned</code>, return <em>the most frequent word that is not banned</em>. It is <strong>guaranteed</strong> there is <strong>at least one word</strong> that is not banned, and that the answer is <strong>unique</strong>.</p>

<p>The words in <code>paragraph</code> are <strong>case-insensitive</strong> and the answer should be returned in <strong>lowercase</strong>.</p>

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

<pre>
<strong>Input:</strong> paragraph = &quot;Bob hit a ball, the hit BALL flew far after it was hit.&quot;, banned = [&quot;hit&quot;]
<strong>Output:</strong> &quot;ball&quot;
<strong>Explanation:</strong> 
&quot;hit&quot; occurs 3 times, but it is a banned word.
&quot;ball&quot; occurs twice (and no other word does), so it is the most frequent non-banned word in the paragraph. 
Note that words in the paragraph are not case sensitive,
that punctuation is ignored (even if adjacent to words, such as &quot;ball,&quot;), 
and that &quot;hit&quot; isn&#39;t the answer even though it occurs more because it is banned.
</pre>

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

<pre>
<strong>Input:</strong> paragraph = &quot;a.&quot;, banned = []
<strong>Output:</strong> &quot;a&quot;
</pre>

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

<ul>
	<li><code>1 &lt;= paragraph.length &lt;= 1000</code></li>
	<li>paragraph consists of English letters, space <code>&#39; &#39;</code>, or one of the symbols: <code>&quot;!?&#39;,;.&quot;</code>.</li>
	<li><code>0 &lt;= banned.length &lt;= 100</code></li>
	<li><code>1 &lt;= banned[i].length &lt;= 10</code></li>
	<li><code>banned[i]</code> consists of only lowercase English letters.</li>
</ul>


class Solution {
public:
    string toLowercase(string &s){
        string t="";
        int n= s.size();
        for(int i=0;i<n; i++){
            if(s[i]>='A' && s[i]<='Z'){
                t+= s[i]-'A'+'a';
            }else{
                t+= s[i];
            }
        }
        return t;
    }
    string mostCommonWord(string paragraph, vector<string>& banned) {

        unordered_map<string,int> mp;
        int n=paragraph.length();
        int i=0;
        string s="";
        while(i<n){
            if(paragraph[i]>='a' && paragraph[i]<='z' || paragraph[i]>='A' && paragraph[i]<='Z'){
                s+=paragraph[i];
                i++;
            }else{
                if(s.length()>0){
                    string str=toLowercase(s);
                    mp[str]++;
                    s="";
                    
                }
                i++;
            }

        }
        if(s.length()>0){
            string str=toLowercase(s);
            mp[str]++;
            s="";
            
        }

   
        string str;
        unordered_set<string>st;
        for(auto x:banned){
            st.insert(x);
        }
        priority_queue<pair<int,string>>pq;
        for(auto it:mp){
            pq.push({it.second,it.first});
        }
        while(!pq.empty()){
            string temp=pq.top().second;
            pq.pop();
            if(st.find(temp)==st.end()){
                return temp;
            }
        }

        return "";

    }
};
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