no message

Author: Chris Wu

problems/minimum-depth-of-binary-tree.py

@@ -0,0 +1,21 @@
+"""
+We use BFS, so as soon as we touch a leaf; we can return it.
+Because BFS traverse the tree level by level. We can be sure that the first leaf we touch is the nearest leaf.
+Note that, a leaf is a node with no children.
+"""
+from collections import deque
+
+class Solution(object):
+    def minDepth(self, root):
+        if not root: return 0
+        q = deque()
+        q.append((root, 1))
+        
+        while q:
+            node, depth = q.popleft()
+            if not node.left and not node.right:
+                return depth
+            if node.left:
+                q.append((node.left, depth+1))
+            if node.right:
+                q.append((node.right, depth+1))