First commit

util/stack.go

@@ -0,0 +1,49 @@
+package util
+
+type (
+	Stack struct {
+		top    *StackNode
+		length int
+	}
+	StackNode struct {
+		value interface{}
+		prev  *StackNode
+	}
+)
+
+// Create a new Stack
+func NewStack() *Stack {
+	return &Stack{nil, 0}
+}
+
+// Return the number of items in the Stack
+func (this *Stack) Len() int {
+	return this.length
+}
+
+// View the top item on the Stack
+func (this *Stack) Peek() interface{} {
+	if this.length == 0 {
+		return nil
+	}
+	return this.top.value
+}
+
+// Pop the top item of the Stack and return it
+func (this *Stack) Pop() interface{} {
+	if this.length == 0 {
+		return nil
+	}
+
+	n := this.top
+	this.top = n.prev
+	this.length--
+	return n.value
+}
+
+// Push a value onto the top of the Stack
+func (this *Stack) Push(value interface{}) {
+	n := &StackNode{value, this.top}
+	this.top = n
+	this.length++
+}