Google Coding Interview Prep - Solve Top Leetcode Problems

Apply flood fill on a grid image by starting from given pixel and changing all connected pixels of same color to a new color using depth-first search in four directions.

Master the maximum sum subarray problem with Kadane's algorithm for the largest contiguous subarray sum. Use a linear approach with current sum and max so far, O(n) time, O(1) space.

tackle the house robber problem by maximizing loot from nonadjacent houses using a memoized dynamic programming approach that decides to rob or skip each house and stores results for efficiency.

Solve the jump game by checking if the last index is reachable from index zero using each position's jump length. Track the max reachable index as you iterate.

Solve the product of array except self using left and right arrays to achieve O(n) time without division.

Group anagrams efficiently by sorting each string, using a hash map to collect strings by their sorted key, and return a list of anagram groups.

Apply a two-pointer approach with a hash table to find the longest substring without repeating characters, expanding when valid and shrinking to remove duplicates, with implementation notes.

Learn to add two numbers represented by nonempty linked lists with digits in reverse order, producing a summed linked list with carries and, if needed, a final node.

Learn the three sum problem by sorting the array and using a two-pointer approach to find all unique triplets that sum to zero, avoiding duplicates; achieve O(n^2) time.

Learn how to perform a binary tree level order traversal using a queue, producing a list of lists where each inner list contains nodes at the same depth.

Find the kth largest element in an array with a min-heap of size k, contrasting sort-based and heap-based approaches and noting the O((n−k) log k) time, O(k) space.

Discover how to solve the coin change problem using dynamic programming to minimize the number of coins. Learn why greedy fails, implement memoization, and analyze time and space complexity.

Explore the longest increasing subsequence problem, define subsequences, and solve with a bottom-up dynamic programming approach using a dp array of length n, achieving O(n^2) time.

Apply a multi-source BFS from all zeros to compute the distance to the nearest zero for every cell in an m by n binary matrix.

Solve the number of islands problem using DFS or BFS. Mark boundary-reachable land cells, then count the remaining land cells that cannot reach the boundary.

Learn the combination sum problem with backtracking: find all combinations of positive candidates that sum to a target, with numbers reusable unlimited times.

Explore generating all subsets of a unique-element array using backtracking to form the power set, by choosing include or exclude for each element, yielding two to the power n subsets.

Explore decoding ways with dynamic programming, counting all valid interpretations of digit strings mapped to letters from 1 to 26, with cross-language implementations.

learn to solve the longest consecutive sequence problem from an unsorted array by using a set to identify sequence starts and count forward for linear time.

Learn to solve the longest palindromic substring with a bottom-up dynamic programming approach: fill a 2D dp table marking palindromes from i to j using the middle subproblem.

Master the maximum subarray problem and apply Kadane's algorithm to find the contiguous subarray with the largest sum. Explore its linear time, constant space implementation across Java, Python, and JavaScript.

Rotate the array to the right by k steps in place with one extra space. Apply a reverse method: reverse whole array, first k, remaining elements, using k mod n.

Solve the set matrix zeroes problem in place by using the first row and column as markers, with booleans to preserve state, achieving constant space.

The sort colors solution uses two pointers to move zeros to the left and twos to the right, leaving ones in the middle, in place.

Explore the spiral matrix problem and master an implementation that traverses any m by n matrix in spiral order, using top, bottom, left, right boundaries and a direction variable.

Validate a sudoku board efficiently by checking rows, columns, and 3x3 grids. Validate only filled cells using a 27-set approach to detect duplicates.

Learn to solve trapping rain water by using left and right maxima for each bar, then sum the water as the min of those maxima minus the bar height.

Master the median from a data stream using two heaps, a max-heap for lower values and a min-heap for upper values, balancing as numbers arrive.

Learn how to merge overlapping intervals in Java by sorting intervals by start times, then end times, and iterating to merge overlaps into non-overlapping intervals.

Learn to merge overlapping intervals using a JavaScript solution. sort intervals by start and end, then merge with a stack-like output to obtain non-overlapping intervals.

Sort intervals by start then end, then merge overlapping intervals into non overlapping ones by comparing with the last interval in the answer, implemented in C++.

solve the merge intervals problem in python by sorting intervals by start (and end), merging overlapping intervals to produce non-overlapping results with o(n log n) time.

Use two binary searches to find the first and last positions of a target in a sorted array, achieving log n time.

Master binary search to find the first and last position of a target in a sorted array using two searches, achieving log n complexity with a JavaScript solution.

Learn to find the first and last positions of a target in a sorted array using two binary searches, achieving log n time in a C++ solution.

Learn to find the first and last positions of a target in a sorted array using two binary searches, achieving log n time and returning -1, -1 when absent.