Leetcode – 968 – Binary Tree Cameras

Given a binary tree, we install cameras on the nodes of the tree. Each camera at a node can monitor its parent, itself, and its immediate children. Calculate the minimum number of cameras needed to monitor all nodes of the tree. Example 1: Input: [0,0,null,0,0]Output: 1 Explanation: One camera is enough to monitor all nodes if placed as … Continue reading Leetcode – 968 – Binary Tree Cameras

Leetcode 99 – Recover Binary Search Tree – Constant space

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Two elements of a binary search tree (BST) are swapped by mistake. Recover the tree without changing its structure with constant space. Example 1: Input: [1,3,null,null,2]   1   / 3   \   2 Output: [3,1,null,null,2]   3   / 1   \   2 Example 2: Input: [3,1,4,null,null,2] 3 / \ 1 4 … Continue reading Leetcode 99 – Recover Binary Search Tree – Constant space

Leetcode 685 – Redundant Connection II

In this problem, a rooted tree is a directed graph such that, there is exactly one node (the root) for which all other nodes are descendants of this node, plus every node has exactly one parent, except for the root node which has no parents. The given input is a directed graph that started as a rooted … Continue reading Leetcode 685 – Redundant Connection II