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Validate Binary Search Tree
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.
参考：http://www.cnblogs.com/remlostime/archive/2012/11/16/2772629.html
这道题的测试用例有点恶心，最后直接全部用long才没有溢出了
1 public class Solution { 2 public boolean isValidBST(TreeNode root) { 3 return isBST(root, ((long)Integer.MIN_VALUE) - 1, ((long)Integer.MAX_VALUE) + 1); 4 } 5 private boolean isBST(TreeNode root, long leftVal,long rightVal){ 6 if(root == null) 7 return true; 8 9 return ((long)root.val) > leftVal && ((long)root.val) < rightVal && isBST(root.left, leftVal, ((long)root.val))10 && isBST(root.right, ((long)root.val), rightVal);11 }12 }
Validate Binary Search Tree
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