力扣819 最常见的单词

思路

代码

class Solution {
public:
    string mostCommonWord(string paragraph, vector<string>& banned) {
        unordered_set<string> bannedSet;
        for (auto & word : banned) {
            bannedSet.emplace(word);
        }
        int maxFrequency = 0;
        unordered_map<string, int> frequencies;
        string word;
        int length = paragraph.size();
        for (int i = 0; i <= length; i++) {
            if (i < length && isalpha(paragraph[i])) {
                word.push_back(tolower(paragraph[i]));
            } else if (word.size() > 0) {
                if (!bannedSet.count(word)) {
                    frequencies[word]++;
                    maxFrequency = max(maxFrequency, frequencies[word]);
                }
                word = "";
            }
        }
        string mostCommon = "";
        for (auto &[word , frequency] : frequencies) {
            if (frequency == maxFrequency) {
                mostCommon = word;
                break;
            }
        }
        return mostCommon;
    }
};