栈

栈的数据结构特点是先进后出，如下图

代码实现

package line
type Stack struct {
    items  []interface{}
    length int
}
func NewStack(cap int) *Stack {
    return &Stack{
        items:  make([]interface{}, 0, cap),
    }
}
func (this *Stack) Push(value interface{}) {
    this.items = append(this.items, value)
    this.length++
}
func (this *Stack) IsEmpty() bool {
    return this.length < 1
}
func (this *Stack) Len() int {
    return this.length
}
func (this *Stack) Cap() int {
    return cap(this.items)
}
func (this *Stack) Top() (value interface{}, exists bool) {
    if this.length < 1 {
        return
    }
    exists = true
    value = this.items[ this.length -1]
    return
}
func (this *Stack) Pop() (value interface{}, exists bool) {
    if this.length < 1 {
        return
    }
    exists = true
    value = this.items[this.length-1]
    this.items = this.items[:this.length -1]
    this.length--
    return
}

测试代码

package line
import "testing"
func TestStack(t *testing.T) {
    stack := NewStack(10)
    empty := stack.IsEmpty()
    if !empty {
        t.Fatalf("want true, got %#v", empty)
    }
    cap := stack.Cap()
    if cap != 10 {
        t.Fatalf("want 10, got %#v", cap)
    }
    stack.Push(45)
    length := stack.Len()
    if length != 1 {
        t.Fatalf("want 1, got %#v", length)
    }
    cap = stack.Cap()
    if cap != 10 {
        t.Fatalf("want 10, got %#v", cap)
    }
    stack.Push(54)
    value, _ := stack.Top()
    if value != 54 {
        t.Fatalf("want 54, got %#v", value)
    }
    value, _ = stack.Pop()
    if value != 54 {
        t.Fatalf("want 54, got %#v", value)
    }
    value, _ = stack.Pop()
    if value != 45 {
        t.Fatalf("want 45, got %#v", value)
    }
    if !stack.IsEmpty() {
        t.Fatalf("want true, got false")
    }
}