2125. Number of Laser Beams in a Bank LeetCode Solution
In this guide, you will get 2125. Number of Laser Beams in a Bank LeetCode Solution with the best time and space complexity. The solution to Number of Laser Beams in a Bank problem is provided in various programming languages like C++, Java, and Python. This will be helpful for you if you are preparing for placements, hackathons, interviews, or practice purposes. The solutions provided here are very easy to follow and include detailed explanations.
Problem Statement of 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.
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.
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'.
Complexity Analysis
Time Complexity: O(mn)
Space Complexity: O(1)
2125. Number of Laser Beams in a Bank LeetCode Solution in C++
class Solution {
public:
int numberOfBeams(vector<string>& bank) {
int ans = 0;
int prevOnes = 0;
for (const string& row : bank) {
const int ones = ranges::count(row, '1');
if (ones > 0) {
ans += prevOnes * ones;
prevOnes = ones;
}
}
return ans;
}
}; /* code provided by PROGIEZ */
2125. Number of Laser Beams in a Bank LeetCode Solution in Java
class Solution {
public int numberOfBeams(String[] bank) {
int ans = 0;
int prevOnes = 0;
for (final String row : bank) {
final int ones = (int) row.chars().filter(c -> c == '1').count();
if (ones > 0) {
ans += prevOnes * ones;
prevOnes = ones;
}
}
return ans;
}
} // code provided by PROGIEZ
2125. Number of Laser Beams in a Bank LeetCode Solution in Python
class Solution:
def numberOfBeams(self, bank: list[str]) -> int:
ans = 0
prevOnes = 0
for row in bank:
ones = row.count('1')
if ones:
ans += prevOnes * ones
prevOnes = ones
return ans # code by PROGIEZ
