819_Most_Common_Word

Author: qiyuangong

README.md

@@ -139,7 +139,8 @@ Remember solutions are only solutions to given problems. If you want full study
 | 581 | [Shortest Unsorted Continuous Subarray](https://leetcode.com/problems/subtree-of-another-tree/description/) | [Python](https://github.com/qiyuangong/leetcode/blob/master/python/581_Shortest_Unsorted_Continuous_Subarray.py) [Java](https://github.com/qiyuangong/leetcode/blob/master/java/581_Shortest_Unsorted_Continuous_Subarray.java) | 1. Sort and find the difference (min and max), O(nlgn)<br>2. Using stack to find boundaries (push when correct order, pop when not correct), O(n) and O(n)<br>3. Find min and max of unordered array, O(n) and O(1)|
 | 617 | [Merge Two Binary Trees](https://leetcode.com/problems/merge-two-binary-trees/description/) | [Python](https://github.com/qiyuangong/leetcode/blob/master/python/617_Merge_Two_Binary_Trees.py) [Java](https://github.com/qiyuangong/leetcode/blob/master/java/617_Merge_Two_Binary_Trees.java) | Traverse both trees Recursion & Iterative (stack) |
 | 771 | [Jewels and Stones](https://leetcode.com/problems/jewels-and-stones/description/) | [Python](https://github.com/qiyuangong/leetcode/blob/master/python/771_Jewels_and_Stones.py) [Java](https://github.com/qiyuangong/leetcode/blob/master/java/771_Jewels_and_Stones.java) | Count given char in string. Hash or table. [Oneline](https://leetcode.com/problems/jewels-and-stones/discuss/113574/1-liners-PythonJavaRuby) |
-| 804 | [Unique Morse Code Words](https://leetcode.com/problems/unique-morse-code-words/description/) | [Python](https://github.com/qiyuangong/leetcode/blob/master/python/771_Jewels_and_Stones.py) [Java](https://github.com/qiyuangong/leetcode/blob/master/java/771_Jewels_and_Stones.java) | String, Hash and Set. Set is recommended. |
+| 804 | [Unique Morse Code Words](https://leetcode.com/problems/unique-morse-code-words/description/) | [Python](https://github.com/qiyuangong/leetcode/blob/master/python/804_Unique_Morse_Code_Words.py) [Java](https://github.com/qiyuangong/leetcode/blob/master/java/804_Unique_Morse_Code_Words.java) | String, Hash and Set. Set is recommended. |
+| 819 | [Most Common Word](https://leetcode.com/problems/unique-morse-code-words/description/) | [Python](https://github.com/qiyuangong/leetcode/blob/master/python/819_Most_Common_Word.py) [Java](https://github.com/qiyuangong/leetcode/blob/master/java/819_Most_Common_Word.java) | String processing, be careful about 'b,b,b'. regex is recommended. |
 | 929 | [Unique Email Addresses](https://leetcode.com/problems/unique-email-addresses/) | [Python](https://github.com/qiyuangong/leetcode/blob/master/python/929_Unique_Email_Addresses.py) [Java](https://github.com/qiyuangong/leetcode/blob/master/java/929_Unique_Email_Addresses.java) | String handle and hash (or set) |
 
 | # | To Understand |

java/819_Most_Common_Word.java

@@ -0,0 +1,34 @@
+class Solution {
+    public String mostCommonWord(String paragraph, String[] banned) {
+        paragraph += ".";
+
+        Set<String> banset = new HashSet();
+        for (String word: banned) banset.add(word);
+        Map<String, Integer> count = new HashMap();
+
+        String ans = "";
+        int ansfreq = 0;
+
+        StringBuilder word = new StringBuilder();
+        for (char c: paragraph.toCharArray()) {
+            if (Character.isLetter(c)) {
+                // word
+                word.append(Character.toLowerCase(c));
+            } else if (word.length() > 0) {
+                // punctuation symbols
+                // node that word length should be larger than 0
+                String finalword = word.toString();
+                if (!banset.contains(finalword)) {
+                    count.put(finalword, count.getOrDefault(finalword, 0) + 1);
+                    // Record max here
+                    if (count.get(finalword) > ansfreq) {
+                        ans = finalword;
+                        ansfreq = count.get(finalword);
+                    }
+                }
+                word = new StringBuilder();
+            }
+        }
+        return ans;
+    }
+}

python/819_Most_Common_Word.py

@@ -0,0 +1,13 @@
+class Solution(object):
+    def mostCommonWord(self, paragraph, banned):
+        """
+        :type paragraph: str
+        :type banned: List[str]
+        :rtype: str
+        """
+        # https://leetcode.com/problems/most-common-word/discuss/193268/python-one-liner
+        banned = set(banned)
+        count = collections.Counter(word for word in re.split('[ !?\',;.]',
+                                    paragraph.lower()) if word)
+        return max((item for item in count.items() if item[0] not in banned),
+                   key=operator.itemgetter(1))[0]