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Validate Binary Search Tree",sidebar_label:"LC98. Validate Binary Search Tree",tags:["Patterns/Tree","DataStructures/Tree"]},s={unversionedId:"QuestionBank/Leetcode/LC98",id:"QuestionBank/Leetcode/LC98",isDocsHomePage:!1,title:"LC98. Validate Binary Search Tree",description:"Problem Description",source:"@site/docs/QuestionBank/Leetcode/98. Validate Binary Search Tree.md",slug:"/QuestionBank/Leetcode/LC98",permalink:"/docs/QuestionBank/Leetcode/LC98",version:"current",sidebar_label:"LC98. Validate Binary Search Tree",sidebar:"Data Structure",previous:{title:"Traversals",permalink:"/docs/DataStructures/Basic/BinaryTree/BSTTraversals"},next:{title:"LC101. Symmetric Tree",permalink:"/docs/QuestionBank/Leetcode/LC101"}},u=[{value:"Problem Description",id:"problem-description",children:[]},{value:"Solution",id:"solution",children:[{value:"High level strategy",id:"high-level-strategy",children:[]},{value:"Code",id:"code",children:[]}]}],d={toc:u};function b(e){var t=e.components,n=Object(a.a)(e,["components"]);return Object(o.b)("wrapper",Object(r.a)({},d,n,{components:t,mdxType:"MDXLayout"}),Object(o.b)("h2",{id:"problem-description"},"Problem Description"),Object(o.b)("p",null,"Source: ",Object(o.b)("a",Object(r.a)({parentName:"p"},{href:"https://leetcode.com/problems/validate-binary-search-tree/"}),"https://leetcode.com/problems/validate-binary-search-tree/")),Object(o.b)("p",null,"Given the root of a binary tree, determine if it is a valid binary search tree (BST)."),Object(o.b)("p",null,"A ",Object(o.b)("strong",{parentName:"p"},"valid BST")," is defined as follows:"),Object(o.b)("ul",null,Object(o.b)("li",{parentName:"ul"},"The left subtree of a node contains only nodes with keys ",Object(o.b)("strong",{parentName:"li"},"less than")," the node's key."),Object(o.b)("li",{parentName:"ul"},"The right subtree of a node contains only nodes with keys ",Object(o.b)("strong",{parentName:"li"},"greater than")," the node's key."),Object(o.b)("li",{parentName:"ul"},"Both the left and right subtrees must also be binary search trees.")),Object(o.b)("p",null,"For example: Given binary tree ","[5, 1, 12, null, null, 15, 16]",","),Object(o.b)("pre",null,Object(o.b)("code",Object(r.a)({parentName:"pre"},{}),"    5\n   / \\\n  1  12\n    /  \\\n   15   16\n")),Object(o.b)("p",null,"return false, since 15 is the left child of 12, but is greater than 12. 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