00_Summary

Summary

Stack: pop, push, peek

HashMap: get, put, containsKey, remove
HashSet: add

LinkedList: peek, add, remove(poll)



String --> substring(beginIndes, endIndex)

beginIndex -- the begin index, inclusive.
endIndex -- the end index, exclusive.


in DFS function, do not use index++, use index+1, should be very careful on this!!! index++ is running then add. if really want to use this, use prefix ++, ++index;

PQ+Comparator:
PriorityQueue<String> pq = new PriorityQueue<String>(new Comparator<String>{
	public int compare(String s, String t){
		return s.compareTo(t);
	}
});

Comparator:
Regular:
Comparator<Developer> byName = new Comparator<Developer>() {
		@Override
		public int compare(Developer o1, Developer o2) {
			return o1.getName().compareTo(o2.getName());
		}
	};

Lamda:
Comparator<Developer> byName = 
		(Developer o1, Developer o2)->o1.getName().compareTo(o2.getName());


Union Find介绍：
		https://github.com/labuladong/fucking-algorithm/blob/master/%E7%AE%97%E6%B3%95%E6%80%9D%E7%BB%B4%E7%B3%BB%E5%88%97/UnionFind%E7%AE%97%E6%B3%95%E8%AF%A6%E8%A7%A3.md