2125. Number of Laser Beams in a Bank
Anti-theft security devices are activated inside a bank. You are given a 0-indexed binary string array bank representing the floor plan of the bank, which is an m x n 2D matrix. bank[i] represents the ith row, consisting of ‘0’s and ‘1’s. ‘0’ means the cell is empty, while’1’ means the cell has a security device.
There is one laser beam between any two security devices if both conditions are met:
- The two devices are located on two different rows: r1 and r2, where r1 < r2.
- For each row i where r1 < i < r2, there are no security devices in the ith row.
Laser beams are independent, i.e., one beam does not interfere nor join with another.
Return the total number of laser beams in the bank.
2130. Maximum Twin Sum of a Linked List
In a linked list of size n, where n is even, the ith node (0-indexed) of the linked list is known as the twin of the (n-1-i)th node, if 0 <= i <= (n / 2) - 1.
- For example, if n = 4, then node 0 is the twin of node 3, and node 1 is the twin of node 2. These are the only nodes with twins for n = 4.
The twin sum is defined as the sum of a node and its twin.
Given the head of a linked list with even length, return the maximum twin sum of the linked list.
1338. Reduce Array Size to The Half
You are given an integer array arr. You can choose a set of integers and remove all the occurrences of these integers in the array.
Return the minimum size of the set so that at least half of the integers of the array are removed.
1414. Find the Minimum Number of Fibonacci Numbers Whose Sum Is K
Given an integer k, return the minimum number of Fibonacci numbers whose sum is equal to k. The same Fibonacci number can be used multiple times.
The Fibonacci numbers are defined as:
- F1 = 1
- F2 = 1
- Fn = Fn-1 + Fn-2 for n > 2.
It is guaranteed that for the given constraints we can always find such Fibonacci numbers that sum up to k.
1351. Count Negative Numbers in a Sorted Matrix
Given a m x n matrix grid which is sorted in non-increasing order both row-wise and column-wise, return the number of negative numbers in grid.