819. 最常见的单词

leetcode-cn.com/problems/mo…

思路:

直接按照题意模拟即可,如果是cpp,就要用双指针算法,来实现字符串分割,如果是java,直接调用spilt即可

class Solution {
public:
unordered_map<string,int> mp;
unordered_map<string,int> ban;
bool check(char c){
    return c>='a'&&c<='z'||c>='A'&&c<='Z';
}
string trans(string s){
    for(auto &it:s){
        if(it>='A'&&it<='Z') it=it-'A'+'a';
    }
    return s;
}
    string mostCommonWord(string paragraph, vector<string>& banned) {
        for(auto &it:banned) ban[it]++;
        for(int i=0;i<paragraph.length();){
            int j=i;
            if(!check(paragraph[j])) {i++;continue;}
            while(j<paragraph.length()&&check(paragraph[j])) j++;
            mp[trans(paragraph.substr(i,j-i))]++;
            i=j;
        }
        string ans;
        int c=-1;
        for(auto &[k,v]:mp){
            if(!ban[k]&&v>c){
                c=v;
                ans=k;
            }
        }

        return ans;
    }
};

class Solution {
    public String mostCommonWord(String paragraph, String[] banned) {
        String[] res=paragraph.split("[^a-zA-Z]");
        HashMap<String,Integer> map=new HashMap<>();
        for (String re : res) {
            if(re.equals("")) continue ;
            re=re.toLowerCase();
            map.put(re,map.getOrDefault(re,0)+1);
        }
        for (String s : banned)  map.remove(s);
        int count=-1;
        String ans="";
        for (Map.Entry<String, Integer> entry : map.entrySet()) {
            if(entry.getValue()>count){
                count=entry.getValue();
                ans=entry.getKey();
            }
        }
        return ans;
    }
}