添加 problem 109

Algorithms/109. Convert Sorted List to Binary Search Tree/109. Convert Sorted List to Binary Search Tree.go

@@ -0,0 +1,57 @@
+package leetcode
+
+/**
+ * Definition for singly-linked list.
+ * type ListNode struct {
+ *     Val int
+ *     Next *ListNode
+ * }
+ */
+/**
+ * Definition for a binary tree node.
+ * type TreeNode struct {
+ *     Val int
+ *     Left *TreeNode
+ *     Right *TreeNode
+ * }
+ */
+
+type TreeNode struct {
+	Val   int
+	Left  *TreeNode
+	Right *TreeNode
+}
+
+func sortedListToBST(head *ListNode) *TreeNode {
+	if head == nil {
+		return nil
+	}
+	if head != nil && head.Next == nil {
+		return &TreeNode{Val: head.Val, Left: nil, Right: nil}
+	}
+	middleNode, preNode := middleNodeAndPreNode(head)
+	if middleNode == nil {
+		return nil
+	}
+	if preNode != nil {
+		preNode.Next = nil
+	}
+	if middleNode == head {
+		head = nil
+	}
+	return &TreeNode{Val: middleNode.Val, Left: sortedListToBST(head), Right: sortedListToBST(middleNode.Next)}
+}
+
+func middleNodeAndPreNode(head *ListNode) (middle *ListNode, pre *ListNode) {
+	if head == nil || head.Next == nil {
+		return nil, head
+	}
+	p1 := head
+	p2 := head
+	for p2.Next != nil && p2.Next.Next != nil {
+		pre = p1
+		p1 = p1.Next
+		p2 = p2.Next.Next
+	}
+	return p1, pre
+}

Algorithms/109. Convert Sorted List to Binary Search Tree/109. Convert Sorted List to Binary Search Tree_test.go

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+package leetcode
+
+import (
+	"fmt"
+	"testing"
+)
+
+type question109 struct {
+	para109
+	ans109
+}
+
+// para 是参数
+// one 代表第一个参数
+type para109 struct {
+	one []int
+}
+
+// ans 是答案
+// one 代表第一个答案
+type ans109 struct {
+	one []int
+}
+
+func Test_Problem109(t *testing.T) {
+
+	qs := []question109{
+
+		question109{
+			para109{[]int{-10, -3, 0, 5, 9}},
+			ans109{[]int{0, -3, 9, -10, -9999, 5}},
+		},
+
+		question109{
+			para109{[]int{-10}},
+			ans109{[]int{-10}},
+		},
+
+		question109{
+			para109{[]int{1, 2}},
+			ans109{[]int{2, 1}},
+		},
+
+		question109{
+			para109{[]int{1, 2, 3}},
+			ans109{[]int{2, 1, 3}},
+		},
+		// question109{
+		// 	para109{[]int{1, 2, 3, 4, 5}, 2, 2},
+		// 	ans109{[]int{1, 2, 3, 4, 5}},
+		// },
+
+		// question109{
+		// 	para109{[]int{1, 2, 3, 4, 5}, 1, 5},
+		// 	ans109{[]int{5, 4, 3, 2, 1}},
+		// },
+
+		// question109{
+		// 	para109{[]int{1, 2, 3, 4, 5, 6}, 3, 4},
+		// 	ans109{[]int{1, 2, 4, 3, 5, 6}},
+		// },
+
+		// question109{
+		// 	para109{[]int{3, 5}, 1, 2},
+		// 	ans109{[]int{5, 3}},
+		// },
+
+		// question109{
+		// 	para109{[]int{3}, 3, 5},
+		// 	ans109{[]int{3}},
+		// },
+	}
+
+	fmt.Printf("------------------------Leetcode Problem 109------------------------\n")
+
+	for _, q := range qs {
+		_, p := q.ans109, q.para109
+		arr := []int{}
+		T2s(sortedListToBST(S2l(p.one)), &arr)
+		fmt.Printf("【input】:%v       【output】:%v\n", p, arr)
+	}
+	fmt.Printf("\n\n\n")
+}

Algorithms/109. Convert Sorted List to Binary Search Tree/README.md

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+# [109. Convert Sorted List to Binary Search Tree](https://leetcode.com/problems/convert-sorted-list-to-binary-search-tree/)
+
+## 题目
+
+Given a singly linked list where elements are sorted in ascending order, convert it to a height balanced BST.
+
+For this problem, a height-balanced binary tree is defined as a binary tree in which the depth of the two subtrees of every node never differ by more than 1.
+
+Example:
+
+```
+Given the sorted linked list: [-10,-3,0,5,9],
+
+One possible answer is: [0,-3,9,-10,null,5], which represents the following height balanced BST:
+
+      0
+     / \
+   -3   9
+   /   /
+ -10  5
+```
+
+
+## 题目大意
+
+将链表转化为高度平衡的二叉搜索树。高度平衡的定义：每个结点的 2 个子结点的深度不能相差超过 1 。
+
+思路比较简单，依次把链表的中间点作为根结点，类似二分的思想，递归排列所有结点即可。