Package g2101_2200.s2125_number_of_laser_beams_in_a_bank

Class Solution

java.lang.Object
g2101_2200.s2125_number_of_laser_beams_in_a_bank.Solution
public class Solution extends java.lang.Object
2125 - Number of Laser Beams in a Bank.

Medium

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.

Example 1:

Input: bank = [“011001”,“000000”,“010100”,“001000”]

Output: 8

Explanation: Between each of the following device pairs, there is one beam. In total, there are 8 beams:

  • bank[0][1] – bank[2][1]

  • bank[0][1] – bank[2][3]

  • bank[0][2] – bank[2][1]

  • bank[0][2] – bank[2][3]

  • bank[0][5] – bank[2][1]

  • bank[0][5] – bank[2][3]

  • bank[2][1] – bank[3][2]

  • bank[2][3] – bank[3][2]

Note that there is no beam between any device on the 0th row with any on the 3rd row.

This is because the 2nd row contains security devices, which breaks the second condition.

Example 2:

Input: bank = [“000”,“111”,“000”]

Output: 0

Explanation: There does not exist two devices located on two different rows.

Constraints:

  • m == bank.length
  • n == bank[i].length
  • 1 <= m, n <= 500
  • bank[i][j] is either '0' or '1'.

  • Constructor Summary

    Constructors
    Constructor
    Description
    Solution()
     

  • Method Summary

    Modifier and Type
    Method
    Description
    int
    numberOfBeams(java.lang.String[] bank)
     

    Methods inherited from class java.lang.Object

    clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

  • Constructor Details

    • Solution

      public Solution()

  • Method Details

    • numberOfBeams

      public int numberOfBeams(java.lang.String[] bank)