g0001_0100.s0098_validate_binary_search_tree.solution.js Maven / Gradle / Ivy

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// #Medium #Top_100_Liked_Questions #Top_Interview_Questions #Depth_First_Search #Tree #Binary_Tree
// #Binary_Search_Tree #Data_Structure_I_Day_14_Tree #Level_1_Day_8_Binary_Search_Tree
// #Udemy_Tree_Stack_Queue #Big_O_Time_O(N)_Space_O(log(N))
// #2024_12_12_Time_0_ms_(100.00%)_Space_53.7_MB_(22.50%)

/**
 * Definition for a binary tree node.
 * function TreeNode(val, left, right) {
 *     this.val = (val===undefined ? 0 : val)
 *     this.left = (left===undefined ? null : left)
 *     this.right = (right===undefined ? null : right)
 * }
 */
/**
 * @param {TreeNode} root
 * @return {boolean}
 */
var isValidBST = function(root) {
    if (root.left == null && root.right == null) { return true }
    return validBST(root, Number.NEGATIVE_INFINITY, Number.POSITIVE_INFINITY)
};

var validBST = function(root, left, right) {
    if (root == null) { return true}
    if (root.val >= right || root.val <= left) { return false }
    return validBST(root.left, left, root.val) && validBST(root.right, root.val, right)
};

export { isValidBST }