819.Most Common Word

819.Most Common Word

难度:Easy

Given a paragraph and a list of banned words, return the most frequent word that is not in the list of banned words. It is guaranteed there is at least one word that isn't banned, and that the answer is unique.

Words in the list of banned words are given in lowercase, and free of punctuation. Words in the paragraph are not case sensitive. The answer is in lowercase.

Example:

Input: 
paragraph = "Bob hit a ball, the hit BALL flew far after it was hit."
banned = ["hit"]
Output: "ball"
Explanation: 
"hit" occurs 3 times, but it is a banned word.
"ball" 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 "ball,"), 
and that "hit" isn't the answer even though it occurs more because it is banned.
 

Note:

1 <= paragraph.length <= 1000.
0 <= banned.length <= 100.
1 <= banned[i].length <= 10.
The answer is unique, and written in lowercase (even if its occurrences in paragraph may have uppercase symbols, and even if it is a proper noun.)
paragraph only consists of letters, spaces, or the punctuation symbols !?',;.
There are no hyphens or hyphenated words.
Words only consist of letters, never apostrophes or other punctuation symbols.

先清洗一下输入数据，利用ban的列表过滤得到新的map，然后找出其中出现次数最多的单词。

class Solution {
public:
    string mostCommonWord(string paragraph, vector<string>& banned) {
        unordered_set<string> ban(banned.begin(),banned.end());
        
        unordered_map<string,int> para_filter;
        string sub;
        int wordCount=0;
        for(auto c:paragraph)
            if(c>='a' && c <='z')
                sub+=c;
        else if(c>='A' &&c<='Z')
            sub+=c+32;
        else
            {
                if(sub=="") continue;
                if(!ban.count(sub))
                    wordCount=max(wordCount,++para_filter[sub]);
                sub="";
            }
      //  cout<<wordCount<<endl;
   //     cout<<para_filter.size()<<endl;
        for(auto p:para_filter)
            if(p.second == wordCount) return p.first;
        return sub;
    }
};

执行用时 :8 ms, 在所有 C++ 提交中击败了86.72%的用户 内存消耗 :8.8 MB, 在所有 C++ 提交中击败了97.33%的用户