验证二叉搜索树

[pwstrick]

98. 验证二叉搜索树

/**
 * Definition for a binary tree node.
 * function TreeNode(val) {
 *     this.val = val;
 *     this.left = this.right = null;
 * }
 */
/**
 * @param {TreeNode} root
 * @return {boolean}
 */
let nodes;
var isValidBST = function(root) {
    nodes = [];
    midOrder(root);
    for(let i=1; i<nodes.length; i++) {
        if(nodes[i] <= nodes[i-1])
            return false;
    }
    return true;
};
//中序遍历
function midOrder(node) {
    if(!node)
        return;
    midOrder(node.left);
    nodes.push(node.val);
    midOrder(node.right);
}