算法：通过递归并限定上下限元素的值的范围可以计算
package com.bupt.acm.leetcode;public class ValidBinary {
private class TreeNode{
int val;
TreeNode left;
TreeNode right;
TreeNode(int x){
val=x;
}
}
public boolean isValidBST(TreeNode root){
if(root==null){
return true;
}
return validBST(root,Integer.MIN_VALUE,Integer.MAX_VALUE);
}
private boolean validBST(TreeNode root, int min, int max) {
// TODO Auto-generated method stub
if(root==null){
return true;
}
if(root.val>min&&root.val<max){
return validBST(root.left,min,root.val)&&validBST(root.right, root.val, max);
}else{
return false;
}
}}
leetcode validBST,布布扣,bubuko.com