problem: 0117 populating next right pointers in each node II

Author: cychiu8

0117 Populating Next Right Pointers in Each Node II/0117 Populating Next Right Pointers in Each Node II.md

@@ -0,0 +1,61 @@
+# 0117. Populating Next Right Pointers in Each Node II
+
+* Difficulty: medium
+* Link: https://leetcode.com/problems/populating-next-right-pointers-in-each-node-ii/
+* Topics: DFS-BFS
+* highlight: 每一次 queue 一開始的長度為同一層 node 的數量
+
+# Clarification
+
+1. Check the inputs and outputs
+    - INPUT: Node
+    - OUTPUT: Node
+
+# Naive Solution
+
+### Thought Process
+
+1. BFS
+- Implement
+    
+    ```python
+    """
+    # Definition for a Node.
+    class Node:
+        def __init__(self, val: int = 0, left: 'Node' = None, right: 'Node' = None, next: 'Node' = None):
+            self.val = val
+            self.left = left
+            self.right = right
+            self.next = next
+    """
+    
+    class Solution:
+        def connect(self, root: 'Node') -> 'Node':
+            if not root:
+                return root
+            
+            q = collections.deque()
+            q.append(root)
+            
+            while q:
+                lenq = len(q)
+                prev = Node(None)
+                for i in range(lenq):
+                    current = q.popleft()
+                    if current.left:
+                        q.append(current.left)
+                    if current.right:
+                        q.append(current.right)
+                    
+                    if prev:
+                        prev.next = current
+                    prev = current
+                prev = None
+            return root
+    ```
+    
+
+### Complexity
+
+- Time complexity: O(N)
+- Space complexity: O(N)