题目：
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 <= 1000.1 <= 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.)paragraphonly 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.
解释：
最开始应该对数据进行清洗，去除标点符号，把大写转换成小写。因为要求出现频率最高的，所以要对字典进行排序。
python代码：
from collections import Counter class Solution: def mostCommonWord(self, paragraph, banned): """ :type paragraph: str :type banned: List[str] :rtype: str """ words=paragraph.replace(',','').replace('.','').replace('!','').replace('?','').replace(':','').replace("'",'').replace(';','').lower().split() _dict=Counter(words) sorted_dict=sorted(_dict.items(),key=lambda x:x[1],reverse=True) # print(sorted_dict) for item in sorted_dict: if item[0] not in banned: return item[0] else: pass 用c++怎么做替换这些操作呢。。。
c++代码：
#include <algorithm> #include <iostream> using namespace std; class Solution { public: string mostCommonWord(string paragraph, vector<string>& banned) { replace(paragraph.begin(),paragraph.end(),',',' '); replace(paragraph.begin(),paragraph.end(),'!',' '); replace(paragraph.begin(),paragraph.end(),'?',' '); replace(paragraph.begin(),paragraph.end(),'.',' '); replace(paragraph.begin(),paragraph.end(),':',' '); replace(paragraph.begin(),paragraph.end(),';',' '); replace(paragraph.begin(),paragraph.end(),'\'',' '); istringstream newstring(paragraph); string word; map<string,int>_map; while(getline(newstring,word,' ')) { //转换大小写 if (word==" ") continue; transform(word.begin(), word.end(), word.begin(), ::tolower); if (!count(banned.begin(),banned.end(),word) &&word!="") { _map[word]+=1; } } int max_count=INT_MIN; string result; for (auto &item:_map) { if (item.second>max_count) { result=item.first; max_count=item.second; } } return result; } }; 总结：
学会c++中<algorithm>中的replace()函数，string自带的replace()函数只能替换第一个还要输入长度反正是不太好用。
注意c++李彪' 要用\'表示。