# LeetCode 1915. Number of Wonderful Substrings

A wonderful string is a string where at most one letter appears an odd number of times.

• For example, `"ccjjc"` and `"abab"` are wonderful, but `"ab"` is not.

Given a string `word` that consists of the first ten lowercase English letters (`'a'` through `'j'`), return the number of wonderful non-empty…

# How to LeetCode — LeetCode Study Plan

Stop the grind. Study with plan! Here’s the patterns that covers 95% of the questions you’ll see on LeetCode.

# Binary Search

Sorted Array

Implicitly Sorted Array

# Depth First Search

The first step to getting a job at Google is to pass the online assessment, commonly referred as “OA”. The OA is given to candidates immediately after your application is approved by the initial screening. If you pass the online assessment, you will move on to the next round which…

The first step to getting a job at Twitter is to pass the online assessment, commonly referred as “OA”. The most common format is a test with two to three questions to complete them within 1–1.5 hours. The assessment result will be used to decide if the candidate can move on to the on-site interviews.

# Amazon Online Assessment Questions

The first step to getting a job at Amazon is to pass the online assessment, commonly referred as “OA”. Candidates are sent a test with 1–2 questions to complete them within 1.5 hours. …

In a string composed of `'L'`, `'R'`, and `'X'` characters, like `"RXXLRXRXL"`, a move consists of either replacing one occurrence of `"XL"` with `"LX"`, or replacing one occurrence of `"RX"` with `"XR"`. …

# LeetCode 222. Count Complete Tree Nodes. Google interview question.

Given a complete binary tree, count the number of nodes.

Note:

Definition of a complete binary tree from Wikipedia:
In a complete binary tree every level, except possibly the last, is completely filled, and all nodes in the last level are as far left as possible. …

# LeetCode 261. Graph Valid Tree

Given `n` nodes labeled from `0` to `n-1` and a list of undirected edges (each edge is a pair of nodes), write a function to check whether these edges make up a valid tree.

Example 1:

`Input: n = 5, and edges = [[0,1], [0,2], [0,3], [1,4]]Output: true`

Example…

## Algo.Monster

10x your algorithm interview prep speed. Take the 5-minute quiz: https://algo.monster/evaluator

Get the Medium app