Add coding exercises for Facebook interviews

Add attempts at solving coding problems to Briefcase.

1 files changed, 70 insertions, 0 deletions

diff --git a/scratch/facebook/balanced-binary-tree.py b/scratch/facebook/balanced-binary-tree.py
new file mode 100644
index 000000000000..afa9706f97ba
--- /dev/null
+++ b/scratch/facebook/balanced-binary-tree.py
@@ -0,0 +1,70 @@
+from collections import deque
+
+class Node(object):
+    # __init__ :: T(A)
+    def __init__(self, value=None, left=None, right=None):
+        self.value = value
+        self.left = left
+        self.right = right
+
+    # insert_left :: T(A) -> A -> T(A)
+    def insert_left(self, value):
+        self.left = Node(value)
+        return self.left
+
+    # insert_right :: T(A) -> A -> T(A)
+    def insert_right(self, value):
+        self.right = Node(value)
+        return self.right
+
+    # is_superbalanced :: T(A) -> Bool
+    def is_superbalanced(self):
+        xs = deque()
+        min_depth, max_depth = float('inf'), float('-inf')
+        xs.append((self, 0))
+        while xs:
+            x, d = xs.popleft()
+            # Only redefine the depths at leaf nodes
+            if not x.left and not x.right:
+                min_depth, max_depth = min(min_depth, d), max(max_depth, d)
+            if x.left:
+                xs.append((x.left, d + 1))
+            if x.right:
+                xs.append((x.right, d + 1))
+        return max_depth - min_depth <= 1
+
+    # __repr__ :: T(A) -> String
+    def __repr__(self):
+        result = ''
+        xs = deque()
+        xs.append((self, 0))
+        while xs:
+            node, indent = xs.popleft()
+            result += '{i}{x}\n'.format(i=' ' * indent, x=node.value)
+            if node.left:
+                xs.append((node.left, indent + 2))
+            if node.right:
+                xs.append((node.right, indent + 2))
+        return result
+
+# from_array :: List(A) -> T(A)
+def from_array(values):
+    xs = deque()
+    root = Node()
+    xs.append(root)
+    for value in values:
+        node = xs.popleft()
+        node.value = value
+        node.left = Node()
+        xs.append(node.left)
+        node.right = Node()
+        xs.append(node.right)
+    return root
+
+x = from_array([1, 1, 1, 1, 1, 1, 1])
+print(x)
+print(x.is_superbalanced())
+
+x = Node(1, Node(2), Node(3))
+print(x)
+print(x.is_superbalanced())