From 3839cde0108bc54a20806b0fe02beeecc49ef436 Mon Sep 17 00:00:00 2001
From: Cool <747682928@qq.com>
Date: Sat, 31 Aug 2024 01:12:56 +0800
Subject: [PATCH] 2024/8/30 LeetCode Hot100 binaryTree
---
.../com/cool/hot100/binary_tree/Num108.java | 23 +++++----
.../com/cool/hot100/binary_tree/Num98.java | 47 +++++++++++++++++++
2 files changed, 62 insertions(+), 8 deletions(-)
create mode 100644 src/main/java/com/cool/hot100/binary_tree/Num98.java
diff --git a/src/main/java/com/cool/hot100/binary_tree/Num108.java b/src/main/java/com/cool/hot100/binary_tree/Num108.java
index 660a15e..69bfa8a 100644
--- a/src/main/java/com/cool/hot100/binary_tree/Num108.java
+++ b/src/main/java/com/cool/hot100/binary_tree/Num108.java
@@ -17,16 +17,23 @@ public class Num108 {
}
public TreeNode buildTree(int[] nums, int start, int end) {
- if(start>=end) return null;
- TreeNode node=new TreeNode();
- int index=(start+end)/2;
- node.val=nums[index];
- node.left=buildTree(nums,start,index-1);
- node.right=buildTree(nums,index+1,end);
+ if (start > end) return null;
+ if(start==end) return new TreeNode(nums[start]);
+ TreeNode node = new TreeNode();
+ if(end-start<2){
+ node.val=nums[end];
+ node.left= new TreeNode(nums[start]);
+ return node;
+ }
+ int index = (start + end) / 2;
+ node.val = nums[index];
+ node.left = buildTree(nums, start, index - 1);
+ node.right = buildTree(nums, index + 1, end);
return node;
}
+
@Test
- public void test(){
- sortedArrayToBST(new int[]{-10,-3,0,5,9});
+ public void test() {
+ sortedArrayToBST(new int[]{-10, -3, 0, 5, 9});
}
}
diff --git a/src/main/java/com/cool/hot100/binary_tree/Num98.java b/src/main/java/com/cool/hot100/binary_tree/Num98.java
new file mode 100644
index 0000000..3502baf
--- /dev/null
+++ b/src/main/java/com/cool/hot100/binary_tree/Num98.java
@@ -0,0 +1,47 @@
+package com.cool.hot100.binary_tree;
+
+import java.util.ArrayList;
+import java.util.List;
+
+/**
+ * Created with IntelliJ IDEA.
+ *
+ * @Author: Cool
+ * @Date: 2024/08/31/0:03
+ * DayNumber 2
+ * Hard 2
+ * Level 3
+ */
+public class Num98 {
+
+
+ public boolean isValidBST(TreeNode root) {
+ if (root == null) return true;
+ return isValidBST(root,Long.MIN_VALUE,Long.MAX_VALUE);
+// List<Integer> list = new ArrayList<>();
+// validBST(root, list);
+// for (int i = 0; i < list.size() - 1; i++) {
+// if (list.get(i) >= list.get(i + 1)) return false;
+// }
+// return true;
+ }
+
+
+ //解法1 中序遍历比较
+ public void validBST(TreeNode root, List<Integer> list) {
+ if (root == null) return;
+ validBST(root.left, list);
+ list.add(root.val);
+ validBST(root.right, list);
+ }
+
+ //解法2
+ public boolean isValidBST(TreeNode root, long start, long end) {
+ if(root==null)return true;
+ if(root.val>start&&root.val<end){
+ return isValidBST(root.left,start,root.val)&&isValidBST(root.right,root.val,end);
+ }
+ return false;
+ }
+
+}