lowest common acestor

src/lowest_common_ancestor.go

@@ -0,0 +1,49 @@
+package src
+
+// 给定一个二叉树, 找到该树中两个指定节点的最近公共祖先
+// 对于有根树 T 的两个节点 p、q，最近公共祖先表示为一个节点 x，
+// 满足 x 是 p、q 的祖先且 x 的深度尽可能大（一个节点也可以是它自己的祖先）
+func lowestCommonAncestor(root, p, q *TreeNode) *TreeNode {
+	return find(root, p.Val, q.Val)
+}
+
+func find(root *TreeNode, l, r int) *TreeNode {
+	if root == nil {
+		return nil
+	}
+	if root.Val == l || root.Val == r {
+		return root
+	}
+
+	left := find(root.Left, l, r)
+	right := find(root.Right, l, r)
+	if left != nil && right != nil {
+		return root
+	}
+
+	if left == nil {
+		return right
+	}
+	return left
+}
+
+// func lowestCommonAncestor(root, p, q *TreeNode) *TreeNode {
+// 	if root == nil {
+// 		return nil
+// 	}
+// 	// p 和 q 均存在于给定的二叉树中
+// 	if root.Val == p.Val || root.Val == q.Val {
+// 		return root
+// 	}
+//
+// 	left := lowestCommonAncestor(root.Left, p, q)
+// 	right := lowestCommonAncestor(root.Right, p, q)
+// 	if left != nil && right != nil {
+// 		return root
+// 	}
+//
+// 	if left != nil {
+// 		return left
+// 	}
+// 	return right
+// }

src/lowest_common_ancestor_test.go

@@ -0,0 +1,25 @@
+package src
+
+import (
+	"fmt"
+	"testing"
+)
+
+func TestLowestCommonAncestor(t *testing.T) {
+	// 初始化二叉树
+	root := &TreeNode{Val: 3}
+	root.Left = &TreeNode{Val: 5}
+	root.Right = &TreeNode{Val: 1}
+	root.Left.Left = &TreeNode{Val: 6}
+	root.Left.Right = &TreeNode{Val: 2}
+	root.Right.Left = &TreeNode{Val: 7}
+	root.Right.Right = &TreeNode{Val: 4}
+
+	fmt.Printf("lowestCommonAncestor of %d and %d is %+v \n", 5, 1, lowestCommonAncestor(root, &TreeNode{Val: 5}, &TreeNode{Val: 1}).Val)
+	fmt.Printf("lowestCommonAncestor of %d and %d is %+v \n", 5, 4, lowestCommonAncestor(root, &TreeNode{Val: 5}, &TreeNode{Val: 4}).Val)
+	fmt.Printf("lowestCommonAncestor of %d and %d is %+v \n", 2, 6, lowestCommonAncestor(root, &TreeNode{Val: 2}, &TreeNode{Val: 6}).Val)
+	fmt.Printf("lowestCommonAncestor of %d and %d is %+v \n", 2, 7, lowestCommonAncestor(root, &TreeNode{Val: 2}, &TreeNode{Val: 7}).Val)
+	fmt.Printf("lowestCommonAncestor of %d and %d is %+v \n", 2, 4, lowestCommonAncestor(root, &TreeNode{Val: 2}, &TreeNode{Val: 4}).Val)
+	fmt.Printf("lowestCommonAncestor of %d and %d is %+v \n", 2, 3, lowestCommonAncestor(root, &TreeNode{Val: 2}, &TreeNode{Val: 3}).Val)
+	fmt.Printf("lowestCommonAncestor of %d and %d is %+v \n", 2, 1, lowestCommonAncestor(root, &TreeNode{Val: 2}, &TreeNode{Val: 1}).Val)
+}

src/node.go

@@ -13,3 +13,16 @@ func (n *ListNode) String() string {
 	}
 	return fmt.Sprintf("{Val:%d Next:%+v}", n.Val, *n.Next)
 }
+
+type TreeNode struct {
+	Val   int
+	Left  *TreeNode
+	Right *TreeNode
+}
+
+func (n *TreeNode) String() string {
+	if n == nil {
+		return "nil"
+	}
+	return fmt.Sprintf("{Val:%d Left:%+v Right:%+v}", n.Val, *n.Left, *n.Right)
+}

src/palindrome_test.go

@@ -0,0 +1,11 @@
+package src
+
+import (
+	"fmt"
+	"testing"
+)
+
+func TestLongestPalindrome(t *testing.T) {
+	s := "babad"
+	fmt.Printf("LongestPalindrome of %s is %s\n", s, LongestPalindrome(s))
+}