## Solved! Leetcode 404. Sum of Left Leaves

Description Sum of Left Leaves Table of ContentsDescription Sum of Left LeavesExample 1Example 2ConstraintsSolutionTime ComplexitySpace Complexity Given the root of a binary tree, return the sum of all left leaves. A leaf is a node with no children. A left leaf is a leaf that is the left child of another node. Example 1 <strong>Input:</strong> root = [3,9,20,null,null,15,7] <strong>Output:</strong> 24 <strong>Explanation:</strong> There ...

## Solved! Leetcode 2073. Time Needed to Buy Tickets

Table of ContentsDescription: Time Needed to Buy TicketsExample 1Example 2ConstraintsSolution 1Time Complexity Space ComplexitySolution 2Time ComplexitySpace Complexity Description: Time Needed to Buy Tickets There are n people in a line queuing to buy tickets, where the 0th person is at the front of the line and the (n - 1)th person is at the back of the line. You are given a 0-indexed integer array tickets of length n where the ...

## Solved! Leetcode 1700. Number of Students Unable to Eat Lunch

Table of ContentsDescription Number of Students Unable to Eat LunchExample 1Example 2ConstraintsSolutionTime ComplexitySpace Complexity Description Number of Students Unable to Eat Lunch The school cafeteria offers circular and square sandwiches at lunch break, referred to by numbers 0 and 1 respectively. All students stand in a queue. Each student either prefers square or circular sandwiches. The number of sandwiches ...

## Leetcode 1167: Minimum Cost to Connect Sticks

You have some number of sticks with positive integer lengths. These lengths are given as an array sticks, where sticks[i] is the length of the ith stick. You can connect any two sticks of lengths x and y into one stick by paying a cost of x + y. You must connect all the sticks until there is only one stick remaining. Return the minimum cost of connecting ...

## Increasing Order Search Tree

Title: Increasing Order Search Tree Source: leetcode.com Given a tree, rearrange the tree in in-order so that the leftmost node in the tree is now the root of the tree, and every node has no left child and only 1 right child (Increasing order search tree). Example 1: Input: [5,3,6,2,4,null,8,1,null,null,null,7,9] 5 / \ 3 6 ...

## Find all Anagrams in a String2

Title: Custom Sort String Source: leetcode.com Given a string s and a non-empty string p, find all the start indices of p‘s anagrams in s. Strings consists of lowercase English letters only and the length of both strings s and p will not be larger than 20,100. The order of output does not matter. Example ...

## Custom Sort String

Title: Custom Sort String Source: leetcode.com S and T are strings composed of lowercase letters. In S, no letter occurs more than once. S was sorted in some custom order previously. We want to permute the characters of T so that they match the order that S was sorted. More specifically, if x occurs before ...

## Monotonic Array

Title: Monotonic Array Source: leetcode.com An array is monotonic if it is either monotone increasing or monotone decreasing. An array A is monotone increasing if for all i <= j, A[i] <= A[j]. An array A is monotone decreasing if for all i <= j, A[i] >= A[j]. Return true if and only if the ...

## Binary Watch Problem

Title: Binary Watch Source: leetcode.com A binary watch has 4 LEDs on the top which represent the hours (0-11), and the 6 LEDs on the bottom represent the minutes (0-59). Each LED represents a zero or one, with the least significant bit on the right. For example, the above binary watch reads “3:25”. Given a ...

## Leaf-Similar trees

Title: Leaf-Similar TreesSource: leetcode.com Consider all the leaves of a binary tree. From left to right order, the values of those leaves form a leaf value sequence. For example, in the given tree above, the leaf value sequence is (6, 7, 4, 9, 8). Two binary trees are considered leaf-similar if their leaf value sequence ...