刷题打卡 －pxu

15. 3Sum . seems no question is easy question. tricky, sort and handle duplication.

such a long day and feel really tired. will prepare the system design interview after show. good night to myself.

Just noticed that I got huge points from the owner of this websites! Great thanks and what a nic day!

completed 138. Copy List with Random Pointer. Easy but still didn't AC. forgot to assign curr = curr.next and hit the time limits. Sigh.

49. Group Anagrams. i got java.lang.UnsupportedOperationException at java.util.AbstractList.add(AbstractList.java:105) when wrote codes like map.put(sorted, Arrays.asList(str)) as the arrays.asList return fixed size arraylist which will fail if new item added. changed to new ArrayList<String>(Arrays.asList(str)) and AC.

notice that for below codes,         
for(Map.Entry<String, List<String>> entry: map.entrySet()){
            res.add(entry.getValue());
        }
it could be replaced as:        
        res.addAll(map.values());

346. Moving Average from Data Stream - seems to be an easier question but I forgot to push data into the queue :(

362. Design Hit Counter . The tricky is using queue.size() and make sure to remove the outdated timestamnp. When doing the while check, make sure check queue is not empty before doing peek(). Cheers!

Spent hours on the word break question. It’s easy to understand using dis with memorization. When it comes to dynamic programming, feel touch to understand it. Hopefully, could figure out later today

Just figure out the dp part of 139. Word Break. what a long day!