涉及知识点

0. 递归
1. golang中struct的定义
2. 切片的初始化(指定类型和长度)
3. 二叉树的实现
4. 验证slice是否是有序列的

验证slice是否是有序列的

1. 手写

//验证函数
func isSort(values []int) bool {
    for i:=1;i<len(values);i++{
            if values[i-1]>values[i]{
                    return false
            }
    }
    return true
}

2. 利用sort库

sort.SliceIsSorted(s, func(i, j int) bool {
   if i<j {
      return true
   }else {
      return false
   }
})

3. 一步搞定 sort.IntsAreSorted(s)

type tree struct{
    value int
    left,right *tree
}

func Sort(values []int){
    var root* tree
    for _,v :=range values {
        root = add(root, v)
    }
    appendValues(values[:0],root)    
}

func appendValues(values []int,t *tree) []int {
    if t!= nil {
        values = appendValues(values, t.left)
        values = append(values, t.value)
        values = appendValues(values, t.right)
     }
     return values
}

func add(t *tree, value int) *tree {
    if t == nil {
        t = new(tree)
        t.value = value
        return t
    }
    if t.value < value {
        t.left = add(t.left,value)
    } else {
        t.right = add(t.right,value)
    }
    return t
 }   

验证函数isSort 中为什么不判定是否为nil,在buildin.go中对len函数的说明可知:Slice, or map: the number of elements in v; if v is nil, len(v) is zero.

// The len built-in function returns the length of v, according to its type:
//	Array: the number of elements in v.
//	Pointer to array: the number of elements in *v (even if v is nil).
//	Slice, or map: the number of elements in v; if v is nil, len(v) is zero.
//	String: the number of bytes in v.
//	Channel: the number of elements queued (unread) in the channel buffer;
//	         if v is nil, len(v) is zero.
// For some arguments, such as a string literal or a simple array expression, the
// result can be a constant. See the Go language specification's "Length and
// capacity" section for details.
func len(v Type) int