Leetcode

Problem Given the root of a binary tree and two integers val and depth, add a row of nodes with value val at the given depth depth. Note that the root node is at depth 1. The adding rule is: Given the integer depth, for each not null tree node cur at the depth depth - 1, create two tree nodes with value val as cur’s left subtree root and right subtree root. cur’s original left subtree should be the left subtree of the new left subtree root. cur’s original right subtree should be the right subtree of the new right subtree root. If depth == 1 that means there is no depth depth - 1 at all, then create a tree node with value val as the new root of the whole original tree, and the original tree is the new root’s left subtree. Examples Example 1: ...

Problem You are given an integer array nums. In one move, you can pick an index i where 0 <= i < nums.length and increment nums[i] by 1. Return the minimum number of moves to make every value in nums unique. The test cases are generated so that the answer fits in a 32-bit integer. Examples Example 1: Input: nums = [1,2,2] Output: 1 Explanation: After 1 move, the array could be [1, 2, 3]. ...

Problem You are given the root of a binary tree and an integer distance. A pair of two different leaf nodes of a binary tree is said to be good if the length of the shortest path between them is less than or equal to distance. Return the number of good leaf node pairs in the tree. Examples Example 1: 1 / \ 2 3 \ 4 ...

Problem Alice has some number of cards and she wants to rearrange the cards into groups so that each group is of size groupSize, and consists of groupSize consecutive cards. Given an integer array hand where hand[i] is the value written on the ith card and an integer groupSize, return true if she can rearrange the cards, or false otherwise. This question is the same as Leetcode 1296: https://leetcode.com/problems/divide-array-in-sets-of-k-consecutive-numbers/, which states: ...

Problem The array-form of an integer num is an array representing its digits in left to right order. For example, for num = 1321, the array form is [1,3,2,1]. Given num, the array-form of an integer, and an integer k, return the array-form of the integer num + k. Examples Example 1: Input: num = [1,2,0,0], k = 34 Output: [1,2,3,4] Explanation: 1200 + 34 = 1234 ...

Problem Given a string expression representing an expression of fraction addition and subtraction, return the calculation result in string format. The final result should be an irreducible fraction. If your final result is an integer, change it to the format of a fraction that has a denominator 1. So in this case, 2 should be converted to 2/1. Examples Example 1: Input: expression = "-1/2+1/2" Output: "0/1" ...

Vertical Order Traversal of a Binary Tree Problem Problem Given the root of a binary tree, calculate the vertical order traversal of the binary tree. For each node at position (row, col), its left and right children will be at positions (row + 1, col - 1) and (row + 1, col + 1) respectively. The root of the tree is at (0, 0). The vertical order traversal of a binary tree is a list of top-to-bottom orderings for each column index starting from the leftmost column and ending on the rightmost column. There may be multiple nodes in the same row and same column. In such a case, sort these nodes by their values. ...

Problem Given the root of an n-ary tree, return the postorder traversal of its nodes’ values. Nary-Tree input serialization is represented in their level order traversal. Each group of children is separated by the null value (See examples) Examples Example 1: graph TD 1 --- A[3] & B[2] & C[4] A --- 5 & 6 (have to use A, B, C in mermaid to make the ordering of nodes better) ...

N-ary Tree Preorder Traversal Problem Problem Given the root of an n-ary tree, return the preorder traversal of its nodes’ values. Nary-Tree input serialization is represented in their level order traversal. Each group of children is separated by the null value (See examples) Examples Example 1: graph TD 1 --- A[3] & B[2] & C[4] A --- 5 & 6 ...

Problem Given a string s and an integer k, reverse the first k characters for every 2k characters counting from the start of the string. If there are fewer than k characters left, reverse all of them. If there are less than 2k but greater than or equal to k characters, then reverse the first k characters and leave the other as original. Examples Example 1: ...