Leetcode Solutions

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  [Solved] Given the root of a binary tree, return the zigzag level order traversal of its nodes’ values. (i.e., from left to right, then right to left for the next level and alternate between).

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  [Solved] Given the root of a binary tree, return the level order traversal of its nodes’ values. (i.e., from left to right, level by level).

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  [Solved] Given the root of a binary tree, check whether it is a mirror of itself (i.e., symmetric around its center).

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  [Solved] Given the roots of two binary trees p and q, write a function to check if they are the same or not. Two binary trees are considered the same if they are structurally identical, and the nodes have the same value.

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  [Solved] Given the root of a binary tree, determine if it is a valid binary search tree (BST).

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  [Solved] Given the root of a binary tree, return the inorder traversal of its nodes’ values.

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  [Solved] Given the head of a singly linked list and two integers left and right where left <= right, reverse the nodes of the list from position left to position right, and return the reversed list.

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  [Solved] You are given two integer arrays nums1 and nums2, sorted in non-decreasing order, and two integers m and n, representing the number of elements in nums1 and nums2 respectively. Merge nums1 and nums2 into a single array sorted in non-decreasing order.

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  [Solved] Given the head of a linked list and a value x, partition it such that all nodes less than x come before nodes greater than or equal to x. You should preserve the original relative order of the nodes in each of the two partitions.

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  [Solved] Given a rows x cols binary matrix filled with 0’s and 1’s, find the largest rectangle containing only 1’s and return its area.

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  [Solved] Given an array of integers heights representing the histogram’s bar height where the width of each bar is 1, return the area of the largest rectangle in the histogram.

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  [Solved] Given the head of a sorted linked list, delete all duplicates such that each element appears only once. Return the linked list sorted as well.

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  [Solved] Given the head of a sorted linked list, delete all nodes that have duplicate numbers, leaving only distinct numbers from the original list. Return the linked list sorted as well.

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  [Solved] Given an integer array nums sorted in non-decreasing order, remove some duplicates in-place such that each unique element appears at most twice. The relative order of the elements should be kept the same.

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  [Solved] Given an array nums with n objects colored red, white, or blue, sort them in-place so that objects of the same color are adjacent, with the colors in the order red, white, and blue. We will use the integers 0, 1, and 2 to represent the color red, white, and blue, respectively.

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  [Solved] Given a string path, which is an absolute path (starting with a slash ‘/’) to a file or directory in a Unix-style file system, convert it to the simplified canonical path.

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  [Solved] 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?

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  [Solved] Given a non-negative integer x, compute and return the square root of x. Since the return type is an integer, the decimal digits are truncated, and only the integer part of the result is returned.

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  [Solved] Given two binary strings a and b, return their sum as a binary string.

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  [Solved] You are given a large integer represented as an integer array digits, where each digits[i] is the ith digit of the integer. The digits are ordered from most significant to least significant in left-to-right order. The large integer does not contain any leading 0’s. Increment the large integer by one and return the resulting array of digits.