feat(solutions): add validate_binary_search_tree

Author: WindomZ

README.md

@@ -34,6 +34,7 @@ If you like it then you can put a :star:**Star** on it.
 
 | # | **Problem** & **Solution** | Difficulty | Single Repetition Duration | LeetCode Run Time |
 | ---: | :----- | :----------: | ----------: | ----------: |
+|[98][Solutions-98]|[Validate Binary Search Tree][Solutions-98-Home]|Medium|[21.0 ns/op][Solutions-98-Code] / [8 test cases][Solutions-98-Test]|8 ms|
 |[96][Solutions-96]|[Unique Binary Search Trees][Solutions-96-Home]|Medium|[39.1 ns/op][Solutions-96-Code] / [6 test cases][Solutions-96-Test]|0 ms|
 |[95][Solutions-95]|[Unique Binary Search Trees II][Solutions-95-Home]|Medium|[259 ns/op][Solutions-95-Code] / [3 test cases][Solutions-95-Test]|48 ms|
 |[94][Solutions-94]|[Binary Tree Inorder Traversal][Solutions-94-Home]|Medium|[119 ns/op][Solutions-94-Code] / [3 test cases][Solutions-94-Test]|0 ms|
@@ -153,6 +154,10 @@ Welcome to report bugs, suggest ideas and discuss on [issues page](https://githu
 ## License
 [![FOSSA Status](https://app.fossa.io/api/projects/git%2Bgithub.com%2FWindomZ%2Fleetcode.go.svg?type=large)](https://app.fossa.io/projects/git%2Bgithub.com%2FWindomZ%2Fleetcode.go?ref=badge_large)
 
+[Solutions-98]:https://leetcode.com/problems/validate-binary-search-tree/
+[Solutions-98-Home]:solutions/validate_binary_search_tree/
+[Solutions-98-Code]:solutions/validate_binary_search_tree/validatebinarysearchtree.go
+[Solutions-98-Test]:solutions/validate_binary_search_tree/validatebinarysearchtree_test.go#L62
 [Solutions-96]:https://leetcode.com/problems/unique-binary-search-trees/
 [Solutions-96-Home]:solutions/unique_binary_search_trees/
 [Solutions-96-Code]:solutions/unique_binary_search_trees/uniquebinarysearchtrees.go

solutions/validate_binary_search_tree/NOTE_Ch-zh.md

@@ -0,0 +1,3 @@
+# 解法要点
+1. BST(binary search trees)是左叶值小于节点值，右叶值大于节点值
+1. 运用DP解法，迭代处理各种情况

solutions/validate_binary_search_tree/README.md

@@ -0,0 +1,36 @@
+# [98. Validate Binary Search Tree](https://leetcode.com/problems/validate-binary-search-tree/description/)
+
+## Description
+
+Given a binary tree, determine if it is a valid binary search tree (BST).
+
+Assume a BST is defined as follows:
+
+*   The left subtree of a node contains only nodes with keys **less than** the node's key.
+*   The right subtree of a node contains only nodes with keys **greater than** the node's key.
+*   Both the left and right subtrees must also be binary search trees.
+
+**Example 1:**  
+```
+    2
+   / \
+  1   3
+```
+
+Binary tree `[2,1,3]`, return true.
+
+**Example 2:**  
+```
+    1
+   / \
+  2   3
+```
+
+Binary tree `[1,2,3]`, return false.
+
+## Solution
+- [Code](validatebinarysearchtree.go)
+- [Testing](validatebinarysearchtree_test.go)
+
+## Note
+- [中文](NOTE_Ch-zh.md)

solutions/validate_binary_search_tree/validatebinarysearchtree.go

@@ -0,0 +1,25 @@
+package validatebinarysearchtree
+
+import "math"
+
+// TreeNode definition for a binary tree node.
+type TreeNode struct {
+	Val   int
+	Left  *TreeNode
+	Right *TreeNode
+}
+
+func isValidBST(root *TreeNode) bool {
+	return validBST(root, math.MinInt64, math.MaxInt64)
+}
+
+func validBST(root *TreeNode, low, high int64) bool {
+	if root == nil {
+		return true
+	}
+	val := int64(root.Val)
+	if val >= high || val <= low {
+		return false
+	}
+	return validBST(root.Left, low, val) && validBST(root.Right, val, high)
+}

solutions/validate_binary_search_tree/validatebinarysearchtree_test.go

@@ -0,0 +1,120 @@
+package validatebinarysearchtree
+
+import (
+	"testing"
+
+	"github.com/WindomZ/testify/assert"
+)
+
+func Test_isValidBST(t *testing.T) {
+	assert.True(t, isValidBST(nil))
+	assert.False(t, isValidBST(&TreeNode{
+		Val: 1,
+		Left: &TreeNode{
+			Val: 1,
+		},
+	}))
+	assert.True(t, isValidBST(&TreeNode{
+		Val: 1,
+		Right: &TreeNode{
+			Val:   2,
+			Right: &TreeNode{Val: 3},
+		},
+	}))
+	assert.True(t, isValidBST(&TreeNode{
+		Val:   2,
+		Left:  &TreeNode{Val: 1},
+		Right: &TreeNode{Val: 3},
+	}))
+	assert.False(t, isValidBST(&TreeNode{
+		Val: 1,
+		Right: &TreeNode{
+			Val:   3,
+			Right: &TreeNode{Val: 2},
+		},
+	}))
+	assert.False(t, isValidBST(&TreeNode{
+		Val: 1,
+		Left: &TreeNode{
+			Val:   3,
+			Right: &TreeNode{Val: 2},
+		},
+	}))
+	assert.False(t, isValidBST(&TreeNode{
+		Val:   1,
+		Left:  &TreeNode{Val: 2},
+		Right: &TreeNode{Val: 3},
+	}))
+	assert.False(t, isValidBST(&TreeNode{
+		Val:   2,
+		Left:  &TreeNode{Val: 3},
+		Right: &TreeNode{Val: 1},
+	}))
+	assert.False(t, isValidBST(&TreeNode{
+		Val: 2,
+		Right: &TreeNode{
+			Val:   3,
+			Right: &TreeNode{Val: 1},
+		},
+	}))
+}
+
+func Benchmark_isValidBST(b *testing.B) {
+	b.StopTimer()
+	b.ReportAllocs()
+	b.StartTimer()
+	b.RunParallel(func(pb *testing.PB) {
+		for pb.Next() {
+			isValidBST(nil)
+			isValidBST(&TreeNode{
+				Val: 1,
+				Left: &TreeNode{
+					Val: 1,
+				},
+			})
+			isValidBST(&TreeNode{
+				Val: 1,
+				Right: &TreeNode{
+					Val:   2,
+					Right: &TreeNode{Val: 3},
+				},
+			})
+			isValidBST(&TreeNode{
+				Val:   2,
+				Left:  &TreeNode{Val: 1},
+				Right: &TreeNode{Val: 3},
+			})
+			isValidBST(&TreeNode{
+				Val: 1,
+				Right: &TreeNode{
+					Val:   3,
+					Right: &TreeNode{Val: 2},
+				},
+			})
+			isValidBST(&TreeNode{
+				Val: 1,
+				Left: &TreeNode{
+					Val:   3,
+					Right: &TreeNode{Val: 2},
+				},
+			})
+			isValidBST(&TreeNode{
+				Val:   1,
+				Left:  &TreeNode{Val: 2},
+				Right: &TreeNode{Val: 3},
+			})
+			isValidBST(&TreeNode{
+				Val:   2,
+				Left:  &TreeNode{Val: 3},
+				Right: &TreeNode{Val: 1},
+			})
+			isValidBST(&TreeNode{
+				Val: 2,
+				Right: &TreeNode{
+					Val:   3,
+					Right: &TreeNode{Val: 1},
+				},
+			})
+		}
+	})
+}