From c50f07c2ac6a4d0c2d0a437618f89f88cb735aad Mon Sep 17 00:00:00 2001
From: Emir Pasic <emirpasic@hotmail.com>
Date: Fri, 13 Mar 2015 23:31:02 +0100
Subject: [PATCH] binary heap (examples and documentation)

---
 README.md              | 52 +++++++++++++++++++++++++++++++++++
 examples/binaryheap.go | 61 ++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 113 insertions(+)
 create mode 100644 examples/binaryheap.go

diff --git a/README.md b/README.md
index 021b7d2..1cc5a1f 100644
--- a/README.md
+++ b/README.md
@@ -22,6 +22,7 @@ Implementation of various data structures in Go.
     - [TreeMap](#treemap)
   - [Trees](#trees)
     - [RedBlackTree](#redblacktree)
+    - [BinaryHeap](#binaryheap)
 - [Functions](#functions)
     - [Comparator](#comparator)
     - [Sort](#sort)
@@ -488,6 +489,57 @@ func main() {
 
 ```
 
+#####BinaryHeap
+
+A binary heap is a heap data structure created using a binary tree. It can be seen as a binary tree with two additional constraints:
+
+- Shape property:
+
+  A binary heap is a complete binary tree; that is, all levels of the tree, except possibly the last one (deepest) are fully filled, and, if the last level of the tree is not complete, the nodes of that level are filled from left to right.
+- Heap property:
+
+  All nodes are either greater than or equal to or less than or equal to each of its children, according to a comparison predicate defined for the heap. <small>[Wiki](http://en.wikipedia.org/wiki/Binary_heap)</small>
+
+  
+
+```go
+package main
+
+import (
+	"github.com/emirpasic/gods/trees/binaryheap"
+	"github.com/emirpasic/gods/utils"
+)
+
+func main() {
+
+	// Min-heap
+	heap := binaryheap.NewWithIntComparator() // empty (min-heap)
+	heap.Push(2)                              // 2
+	heap.Push(3)                              // 2, 3
+	heap.Push(1)                              // 1, 3, 2
+	heap.Values()                             // 1, 3, 2
+	_, _ = heap.Peek()                        // 1,true
+	_, _ = heap.Pop()                         // 1, true
+	_, _ = heap.Pop()                         // 2, true
+	_, _ = heap.Pop()                         // 3, true
+	_, _ = heap.Pop()                         // nil, false (nothing to pop)
+	heap.Push(1)                              // 1
+	heap.Clear()                              // empty
+	heap.Empty()                              // true
+	heap.Size()                               // 0
+
+	// Max-heap
+	inverseIntComparator := func(a, b interface{}) int {
+		return -utils.IntComparator(a, b)
+	}
+	heap = binaryheap.NewWith(inverseIntComparator) // empty (min-heap)
+	heap.Push(2)                                    // 2
+	heap.Push(3)                                    // 3, 2
+	heap.Push(1)                                    // 3, 2, 1
+	heap.Values()                                   // 3, 2, 1
+}
+```
+
 ### Functions
 
 Various helper functions used throughout the library.
diff --git a/examples/binaryheap.go b/examples/binaryheap.go
new file mode 100644
index 0000000..588ce5b
--- /dev/null
+++ b/examples/binaryheap.go
@@ -0,0 +1,61 @@
+/*
+Copyright (c) 2015, Emir Pasic
+All rights reserved.
+
+Redistribution and use in source and binary forms, with or without
+modification, are permitted provided that the following conditions are met:
+
+* Redistributions of source code must retain the above copyright notice, this
+  list of conditions and the following disclaimer.
+
+* Redistributions in binary form must reproduce the above copyright notice,
+  this list of conditions and the following disclaimer in the documentation
+  and/or other materials provided with the distribution.
+
+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+*/
+
+package examples
+
+import (
+	"github.com/emirpasic/gods/trees/binaryheap"
+	"github.com/emirpasic/gods/utils"
+)
+
+func BinaryHeapExample() {
+
+	// Min-heap
+	heap := binaryheap.NewWithIntComparator() // empty (min-heap)
+	heap.Push(2)                              // 2
+	heap.Push(3)                              // 2, 3
+	heap.Push(1)                              // 1, 3, 2
+	heap.Values()                             // 1, 3, 2
+	_, _ = heap.Peek()                        // 1,true
+	_, _ = heap.Pop()                         // 1, true
+	_, _ = heap.Pop()                         // 2, true
+	_, _ = heap.Pop()                         // 3, true
+	_, _ = heap.Pop()                         // nil, false (nothing to pop)
+	heap.Push(1)                              // 1
+	heap.Clear()                              // empty
+	heap.Empty()                              // true
+	heap.Size()                               // 0
+
+	// Max-heap
+	inverseIntComparator := func(a, b interface{}) int {
+		return -utils.IntComparator(a, b)
+	}
+	heap = binaryheap.NewWith(inverseIntComparator) // empty (min-heap)
+	heap.Push(2)                                    // 2
+	heap.Push(3)                                    // 3, 2
+	heap.Push(1)                                    // 3, 2, 1
+	heap.Values()                                   // 3, 2, 1
+}