🚧 [98]

Author: enkr1

98/my_solution.js

@@ -0,0 +1,73 @@
+class TreeNode {
+  constructor(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) {
+  let leftAncestors = [], rightAncestors = [];
+
+  const exploreLeft = (node, list) => {
+    console.log(`exploreLeft`)
+    console.log(node.val)
+    // console.log(leftAncestors.concat([node.val]))
+    // console.log(Math.min(...leftAncestors.concat([node.val])))
+    // console.log(node.val !== Math.min(leftAncestors.concat([node.val])))
+    if (node.val !== Math.min(...leftAncestors.concat([node.val]))) return false;
+    leftAncestors.push(node.val);
+
+    return true || exploreRight(node, list);
+  }
+
+  const exploreRight = (node, list) => {
+    console.log(`exploreRight`)
+    console.log(node.val)
+    console.log(rightAncestors)
+    if (node.val !== Math.max(...rightAncestors.concat([node.val]))) return false;
+    rightAncestors.push(node.val);
+    return true || exploreLeft(node, list);
+  }
+
+  let queue = [root];
+
+  while (queue.length > 0) {
+    let curr = queue.shift(), left = curr.left, right = curr.right;
+
+    if ((left?.val ?? -Infinity) >= curr.val || (right?.val ?? Infinity) <= curr.val) return false;
+
+    if (null !== left) {
+      queue.push(left);
+      if (!exploreLeft(left, leftAncestors)) return false;
+    }
+
+
+    if (null !== right) {
+      queue.push(right);
+      if (!exploreRight(right, rightAncestors)) return false;
+    }
+  }
+
+  return true;
+};
+
+// [3,1,5,0,2,4,6]
+let x =
+  isValidBST(new TreeNode(3,
+    new TreeNode(1,
+      new TreeNode(0),
+      new TreeNode(2)
+    ),
+    new TreeNode(5,
+      new TreeNode(4),
+      new TreeNode(6)
+    )
+  ))
+
+console.log("Result")
+console.log(x)

98/solution.js

@@ -0,0 +1,48 @@
+class TreeNode {
+  constructor(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) {
+  let leftAncestors = [], rightAncestors = [];
+
+  const exploreLeft = (node) => {
+    if (node.val !== Math.min(leftAncestors.concat([node.val]))) return false;
+    leftAncestors.push(node.val);
+    return true;
+  }
+
+  const exploreRight = (node) => {
+    if (node.val !== Math.max(rightAncestors.concat([node.val]))) return false;
+    rightAncestors.push(node.val);
+    return true;
+  }
+
+  let queue = [root];
+
+  while (queue.length > 0) {
+    let curr = queue.shift(), left = curr.left, right = curr.right;
+
+    if ((left?.val ?? -Infinity) >= curr.val || (right?.val ?? Infinity) <= curr.val) return false;
+
+    if (null !== left) {
+      queue.push(left);
+      if (!exploreLeft(left)) return false;
+    }
+
+
+    if (null !== right) {
+      queue.push(right);
+      if (!exploreRight(right)) return false;
+    }
+  }
+
+  return true;
+};

README.md

@@ -36,6 +36,7 @@
 - [76. Minimum Window Substring](./76/)
 - [79. Word Search](./79/)
 - [83. Remove Duplicates from Sorted List](./83/)
+- [98. Validate Binary Search Tree](./98/)
 - [100. Same Tree](./100/)
 - [102. Binary Tree Level Order Traversal](./102/)
 - [104. Maximum Depth of Binary Tree](./104/)
@@ -143,7 +144,7 @@ Batch create:
 NOTE: JS IS HERE
 -->
 ```ssh
-chapter=105 && mkdir ./$chapter && touch ./$chapter/my_solution.js && touch ./$chapter/solution.js && alias x="node ./$chapter/my_solution.js"
+chapter=98 && mkdir ./$chapter && touch ./$chapter/my_solution.js && touch ./$chapter/solution.js && alias x="node ./$chapter/my_solution.js"
 ```
 > then you can use `x` for quick debug.