Question 655. Print Binary Tree Print a binary tree in an m*n 2D string array following these rules: The row number m should be equal to the height of the given binary tree. The column number n should always be an odd number. The root node’s value (in string format) should be put in the exactly middle of the first row it can be put. The column and the row where the root node belongs will separate the rest space into two parts (left-bottom part and right-bottom part).

Question 117. Populating Next Right Pointers in Each Node II Given a binary tree struct Node { int val; Node *left; Node *right; Node *next; } Populate each next pointer to point to its next right node. If there is no next right node, the next pointer should be set to NULL. Initially, all next pointers are set to NULL. Follow up: You may only use constant extra space.

Question 134. Gas Station There are N gas stations along a circular route, where the amount of gas at station i is gas[i]. You have a car with an unlimited gas tank and it costs cost[i] of gas to travel from station i to its next station (i+1). You begin the journey with an empty tank at one of the gas stations. Return the starting gas station’s index if you can travel around the circuit once in the clockwise direction, otherwise return -1.

Question Leetcode 962. Maximum Width Ramp Given an array A of integers, a ramp is a tuple (i, j) for which i < j and A[i] <= A[j]. The width of such a ramp is j - i. Find the maximum width of a ramp in A. If one doesn’t exist, return 0. Note: 2 <= A.length <= 50000 0 <= A[i] <= 50000 Examples: Example 1: Input: [6,0,8,2,1,5] Output: 4 Explanation: The maximum width ramp is achieved at (i, j) = (1, 5): A[1] = 0 and A[5] = 5.

Question 955. Delete Columns to Make Sorted II We are given an array A of N lowercase letter strings, all of the same length. Now, we may choose any set of deletion indices, and for each string, we delete all the characters in those indices. For example, if we have an array A = ["abcdef","uvwxyz"] and deletion indices {0, 2, 3}, then the final array after deletions is ["bef","vyz"].