/
isBST
51 lines (36 loc) · 1021 Bytes
/
isBST
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
/**
* Definition for a binary tree node.
* public class TreeNode {
* int val;
* TreeNode left;
* TreeNode right;
* TreeNode(int x) { val = x; }
* }
*/
public class Solution {
TreeNode prev = null;
public boolean isValidBST(TreeNode root) {
if(root == null) return true;
//Traverse in Inorder Fashion
if(!isValidBST(root.left)){
return false;
}
if(prev != null && root.val <= prev.val){
return false;
}
prev = root;
return isValidBST(root.right);
}
}
public class Solution {
public boolean isValidBST(TreeNode root) {
return isValidBST(root, Long.MIN_VALUE , Long.MAX_VALUE);
}
private boolean isValidBST(TreeNode root, long min, long max) {
if(root == null) return true ;
if(root.val <= min || root.val >= max){
return false;
}
return isValidBST(root.left, min, root.val) && isValidBST(root.right, root.val, max);
}
}