From a39aea354b071612c071d98125e879fe14c76a54 Mon Sep 17 00:00:00 2001
From: Joe Zhao <ztuowen@gmail.com>
Date: Mon, 13 Apr 2015 15:21:21 +0800
Subject: +61 +62 +63

---
 H61.hs   |  5 +++++
 H62.hs   | 14 ++++++++++++++
 H63.hs   |  8 ++++++++
 Tree4.hs |  6 ++++++
 4 files changed, 33 insertions(+)
 create mode 100644 H61.hs
 create mode 100644 H62.hs
 create mode 100644 H63.hs
 create mode 100644 Tree4.hs

diff --git a/H61.hs b/H61.hs
new file mode 100644
index 0000000..64dd9e3
--- /dev/null
+++ b/H61.hs
@@ -0,0 +1,5 @@
+import Tree
+
+countLeaves Empty = 0
+countLeaves (Branch _ Empty Empty) = 1
+countLeaves (Branch _ t1 t2) = countLeaves t1 + countLeaves t2
diff --git a/H62.hs b/H62.hs
new file mode 100644
index 0000000..b835b20
--- /dev/null
+++ b/H62.hs
@@ -0,0 +1,14 @@
+import Tree
+-- import Tree4
+
+leaves Empty = []
+leaves (Branch x Empty Empty) = [x]
+leaves (Branch x t1 t2) = leaves t1 ++ leaves t2
+
+internals Empty = []
+internals (Branch x Empty Empty) = []
+internals (Branch x t1 t2) = [x] : internals t1 ++ internals t2
+
+atLevel Empty _ = []
+atLevel (Branch x _ _) 1 = [x]
+atLevel (Branch _ t1 t2) n = atLevel t1 (n-1) ++ atLevel t2 (n-1)
diff --git a/H63.hs b/H63.hs
new file mode 100644
index 0000000..03f081e
--- /dev/null
+++ b/H63.hs
@@ -0,0 +1,8 @@
+import Tree
+
+completeBinaryTree n = makeTree 1
+    where makeTree x
+            | x > n = Empty
+            | otherwise = Branch 'x' (makeTree (2*x)) (makeTree (2*x+1))
+
+isCompleteBinaryTree
diff --git a/Tree4.hs b/Tree4.hs
new file mode 100644
index 0000000..533899c
--- /dev/null
+++ b/Tree4.hs
@@ -0,0 +1,6 @@
+module Tree4 where
+
+import Tree
+
+tree4 = Branch 1 (Branch 2 Empty (Branch 4 Empty Empty))
+                 (Branch 2 Empty Empty)
-- 
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