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98.java
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98.java
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__________________________________________________________________________________________________
sample 0 ms submission
/**
* Definition for a binary tree node.
* public class TreeNode {
* int val;
* TreeNode left;
* TreeNode right;
* TreeNode(int x) { val = x; }
* }
*/
class Solution {
public boolean isValidBST(TreeNode root) {
if(root == null){
return true;
}
return helper(root,Long.MIN_VALUE,Long.MAX_VALUE);
}
public boolean helper(TreeNode root, long leftBound, long rightBound){
if(root == null){
return true;
}
if(root.val <= leftBound || root.val >= rightBound){
return false;
}
return helper(root.left,leftBound,root.val) && helper(root.right,root.val,rightBound);
}
}
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sample 34512 kb submission
/**
* Definition for a binary tree node.
* public class TreeNode {
* int val;
* TreeNode left;
* TreeNode right;
* TreeNode(int x) { val = x; }
* }
*/
class Solution {
public boolean isValidBST(TreeNode root) {
int[] result= validateNode(root , null);
return result[0] == 1;
}
private int[] validateNode(TreeNode node, TreeNode parent) {
if(node !=null){
int[] l = validateNode(node.left, node);
int[] r = validateNode(node.right, node);
if(l[0]==1 && r[0]==1) {
if((node.left ==null || l[2]<node.val) && (node.right==null|| r[1]>node.val)) {
return new int[]{1, l[1], r[2]};
}else {
return new int[]{0,0,0};
}
}else {
return new int[]{0,0,0};
}
}else if(parent!= null) {
return new int[]{1, parent.val, parent.val};
}
return new int[]{1,0,0};
}
}
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