class Solution {

// Time: O(P+B),where P is the size of paragraph and B is the size of banned.

// Space: O(P+B), to store the count and the banned set.

public String mostCommonWord(String paragraph, String[] banned) {

// split paragraph

String[] words = paragraph.toLowerCase().split("\\W+");

// add banned words to set

Set<String> set = new HashSet<>();

for(String word : banned){

set.add(word);

}

// add paragraph words to hash map

Map<String, Integer> map = new HashMap<>();

for(String word : words){

if(!set.contains(word)){

map.put(word, map.getOrDefault(word, 0) + 1);

}

}

// get the most frequent word

int max = 0; // max frequency

String res = "";

for(String str : map.keySet()){

if(map.get(str) > max){

max = map.get(str);

res = str;

}

}

return res;

}

}