2218. Maximum Value of K Coins From Piles

There are n piles of coins on a table. Each pile consists of a positive number of coins of assorted denominations.

In one move, you can choose any coin on top of any pile, remove it, and add it to your wallet.

Given a list piles, where piles[i] is a list of integers denoting the composition of the ith pile from top to bottom, and a positive integer k, return the maximum total value of coins you can have in your wallet if you choose exactly k coins optimally.

1820. Maximum Number of Accepted Invitations

There are m boys and n girls in a class attending an upcoming party.

You are given an m x n integer matrix grid, where grid[i][j] equals 0 or 1. If grid[i][j] == 1, then that means the ith boy can invite the jth girl to the party. A boy can invite at most one girl, and a girl can accept at most one invitation from a boy.

Return the maximum possible number of accepted invitations.

2184. Number of Ways to Build Sturdy Brick Wall

You are given integers height and width which specify the dimensions of a brick wall you are building. You are also given a 0-indexed array of unique integers bricks, where the ith brick has a height of 1 and a width of bricks[i]. You have an infinite supply of each type of brick and bricks may not be rotated.

Each row in the wall must be exactly width units long. For the wall to be sturdy, adjacent rows in the wall should not join bricks at the same location, except at the ends of the wall.

Return the number of ways to build a sturdy wall. Since the answer may be very large, return it modulo 109 + 7.

1855. Maximum Distance Between a Pair of Values

You are given two non-increasing 0-indexed integer arrays nums1​​​​​​ and nums2​​​​​​.

A pair of indices (i, j), where 0 <= i < nums1.length and 0 <= j < nums2.length, is valid if both i <= j and nums1[i] <= nums2[j]. The distance of the pair is j - i​​​​.

Return the maximum distance of any valid pair (i, j). If there are no valid pairs, return 0.

An array arr is non-increasing if arr[i-1] >= arr[i] for every 1 <= i < arr.length.

2174. Remove All Ones With Row and Column Flips II

You are given a 0-indexed m x n binary matrix grid.

In one operation, you can choose any i and j that meet the following conditions:

• 0 <= i < m
• 0 <= j < n
• grid[i][j] == 1

and change the values of all cells in row i and column j to zero.

Return the minimum number of operations needed to remove all 1’s from grid.

2083. Substrings That Begin and End With the Same Letter

You are given a 0-indexed string s consisting of only lowercase English letters. Return the number of substrings in s that begin and end with the same character.

A substring is a contiguous non-empty sequence of characters within a string.

1062. Longest Repeating Substring

Given a string s, return the length of the longest repeating substrings. If no repeating substring exists, return 0.

1682. Longest Palindromic Subsequence II

A subsequence of a string s is considered a good palindromic subsequence if:

• It is a subsequence of s.
• It is a palindrome (has the same value if reversed).
• It has an even length.
• No two consecutive characters are equal, except the two middle ones.

For example, if s = “abcabcabb”, then “abba” is considered a good palindromic subsequence, while “bcb” (not even length) and “bbbb” (has equal consecutive characters) are not.

Given a string s, return the length of the longest good palindromic subsequence in s.

1886. Determine Whether Matrix Can Be Obtained By Rotation

Given two n x n binary matrices mat and target, return true if it is possible to make mat equal to target by rotating mat in 90-degree increments, or false otherwise.

572. Subtree of Another Tree

Given the roots of two binary trees root and subRoot, return true if there is a subtree of root with the same structure and node values of subRoot and false otherwise.

A subtree of a binary tree tree is a tree that consists of a node in tree and all of this node’s descendants. The tree tree could also be considered as a subtree of itself.