<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:
    bool isSplitter(char c){
        string splitters = " !?',;.";
        for(char sp:splitters){
            if(c==sp)return true;
        }
        return false;
    }
    vector<string> splitWords(string para){
        string word = "";
        vector<string> ws;
        for(int i=0;i<para.size();++i){
            if(isSplitter(para[i])){
                if(word!="") ws.push_back(word);
                word="";
            }
            else{
                if('A' <= para[i] && para[i]<='Z'){
                    word += 'a' + (para[i]-'A');
                }else{
                    word+=para[i];
                }
            }
        }
        if(word!="") ws.push_back(word);
        return ws;
    }
    string mostCommonWord(string paragraph, vector<string>& banned) {
        map<string, bool> bmap;
        for(string&b:banned)bmap[b] = true;
        vector<string> words = splitWords(paragraph);
        map<string, int> dict;
        for(string w:words){
            if(bmap[w])continue;
            dict[w]++;
        }
        int mx=0;
        string ans ="";
        for(auto d:dict){
            if(d.second > mx) ans = d.first, mx = d.second;
        }
        return ans;
    }
};
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