## Important and Useful links from all over the Leetcode

List of all good posts on Leetcode. Comment down whichever I am missing and I will add all of them here – DP for beginners by @wh0ami – https://leetcode.com/discuss/general-discussion/662866/dp-for-beginners-problems-patterns-sample-solutions[LIST – https://leetcode.com/list/x1k8lxi5] Graph for beginners by @wh0ami – https://leetcode.com/discuss/general-discussion/655708/graph-for-beginners-problems-pattern-sample-solutions/562734[LIST – https://leetcode.com/list/x1wy4de7] Sliding window for beginners by @wh0ami – https://leetcode.com/discuss/general-discussion/657507/sliding-window-for-beginners-problems-template-sample-solutions/562721[LIST – https://leetcode.com/list/x1lbzfk3] DP Patterns by @aatalyk – https://leetcode.com/discuss/general-discussion/458695/dynamic-programming-patterns Leetcode patterns from edu_cative_dot_io by @late_riser […]

## 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 […]

## Leetcode 99 – Recover Binary Search Tree – Constant space

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 […]