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Two elements of a binary search tree (BST) are swapped by mistake.Recover the tree without changing its structure.Example 1:Input: [1,3,null,null,2] 1 / 3 \ 2Output: [3,1,null,null,2]...

Given a non-empty binary tree, find the maximum path sum.For this problem, a path is defined as any sequence of nodes from some starting node to any node in the tree along the parent-child connection...

Given a complete binary tree, count the number of nodes.Note:Definition of a complete binary tree from Wikipedia:In a complete binary tree every level, except possibly the last, is completely fille...

Given a binary tree, find the length of the longest path where each node in the path has the same value. This path may or may not pass through the root.Note: The length of path between two nodes is r...

Given an integer n, generate all structurally unique BST’s (binary search trees) that store values 1 … n.Example:Input: 3Output:[ [1,null,3,2], [3,2,null,1], [3,1,null,null,2], [2,1,3], ...