记录贴，互勉

138. Copy List with Random Pointer
Use map to copy the node and find the next and random new node from map.

200. Number of Islands
1. Find "1" in the map
2. Search all the '1' in the same island and change it to '0';
Hint: Check the bounds of the map.

547. Number of Provinces
Check connected use visited array

695. Max Area of Island

733. Flood Fill

827. Making A Large Island
1. Count area of each island and change the value, map it
2. Find the 0 and find the four different direction's island's area add them up

1136. Parallel Course

Topologic sort, indegree.

Only when indegree is 0, can node enque

1162. As Far from Land as Possible
use class to mark down the max step.

841. Keys and Rooms
DFS search

1202. Smallest String With Swaps
union-find