Minimum Depth of Binary Tree Problem Given a binary tree, find its minimum depth. The minimum depth is the number of nodes along the shortest path from the root node down to the nearest leaf node. Note: A leaf is a node with no children. Examples Example 1: graph TD; 3 --- 9 & 20; 20 --- 15 & 7; ...
Minimum Absolute Difference in BST Problem Problem Given the root of a Binary Search Tree (BST), return the minimum absolute difference between the values of any two different nodes in the tree. OR Given the root of a Binary Search Tree (BST), return the minimum difference between the values of any two different nodes in the tree. Examples Example 1: graph TB; 4 --- 2 & 6; 2 --- 1 & 3; ...
Problem Given an integer n, return true if n is a perfect number, otherwise return false. Definition A perfect number is a natural number that is equal to the sum of its positive divisors, excluding the number itself. A divisor of an integer x is an integer that can divide x evenly. The first perfect numbers are 6, 28, 496, 8128 and all of them are in form $$ 2^{n-1}.(2^n - 1)$$ ...
Problem Given an integer numRows, return the first numRows of Pascal’s triangle. Examples Example 1: ...
Transpose a Matrix Problem Given a 2D integer array matrix, return the transpose of matrix. The transpose of a matrix is the matrix flipped over its main diagonal, switching the matrix’s row and column indices. Example Example 1: $$ \begin{bmatrix} \colorbox{red} 1 & \colorbox{red} 2 & \colorbox{red}3 \\ \colorbox{green} 4 & \colorbox{green} 5 & \colorbox{green}6 \\ \colorbox{blue} 7 & \colorbox{blue} 8 & \colorbox{blue}9 \end{bmatrix} \Longrightarrow \begin{bmatrix} \colorbox{red} 1 & \colorbox{green} 4 & \colorbox{blue} 7 \\ \colorbox{red} 2 & \colorbox{green} 5 & \colorbox{blue} 8 \\ \colorbox{red} 3 & \colorbox{green} 6 & \colorbox{blue} 9 \end{bmatrix} $$ ...
Problem Given a binary tree, write a non recursive or iterative algorithm for Inorder traversal. Inorder Traversal First, visit all the nodes in the left subtree Then the root node Visit all the nodes in the right subtree inorder(root->left) display(root->data) inorder(root->right) Example Example 1: 1 \ 2 / 3 ...
Problem Given a string s containing just the characters '(', ')', '{', '}', '[' and ']', determine if the input string is valid. An input string is valid if: Open brackets must be closed by the same type of brackets. Open brackets must be closed in the correct order. Every close bracket has a corresponding open bracket of the same type. Examples Example 1: ...
Problem You are given an array of integers stones where stones[i] is the weight of the ith stone. We are playing a game with the stones. On each turn, we choose the heaviest two stones and smash them together. Suppose the heaviest two stones have weights x and y with x <= y. The result of this smash is: If x == y, both stones are destroyed, and If x != y, the stone of weight x is destroyed, and the stone of weight y has new weight y - x. At the end of the game, there is at most one stone left. ...
Problem You are climbing a staircase. It takes n steps to reach the top. Each time you can either climb 1 or 2 steps. In how many distinct ways can you climb to the top? OR There are n stairs, a person standing at the bottom wants to reach the top. The person can climb either 1 stair or 2 stairs at a time. Count the number of ways, the person can reach the top. ...
Problem Given the heads of two singly linked-lists headA and headB, return the node at which the two lists intersect. If the two linked lists have no intersection at all, return null. Intersection point means end of one linked list is linked with some node in another linked list and it forms a Y shape. Input: Two Linked List Output: Intersection Node or point, find Intersection Point in Two Linked List ...