2125. Number of Laser Beams in a Bank: AC

Author: tan-wei

src/solution/mod.rs

@@ -1604,3 +1604,4 @@ mod s2120_execution_of_all_suffix_instructions_staying_in_a_grid;
 mod s2121_intervals_between_identical_elements;
 mod s2122_recover_the_original_array;
 mod s2124_check_if_all_as_appears_before_all_bs;
+mod s2125_number_of_laser_beams_in_a_bank;

src/solution/s2125_number_of_laser_beams_in_a_bank.rs

@@ -0,0 +1,86 @@
+/**
+ * [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 i^th 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 i^th 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:
+ * <img alt="" src="https://assets.leetcode.com/uploads/2021/12/24/laser1.jpg" style="width: 400px; height: 368px;" />
+ * 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 0^th row with any on the 3^rd row.
+ * This is because the 2^nd row contains security devices, which breaks the second condition.
+ *
+ * Example 2:
+ * <img alt="" src="https://assets.leetcode.com/uploads/2021/12/24/laser2.jpg" style="width: 244px; height: 325px;" />
+ * 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'.
+ *
+ */
+pub struct Solution {}
+
+// problem: https://leetcode.com/problems/number-of-laser-beams-in-a-bank/
+// discuss: https://leetcode.com/problems/number-of-laser-beams-in-a-bank/discuss/?currentPage=1&orderBy=most_votes&query=
+
+// submission codes start here
+
+impl Solution {
+    pub fn number_of_beams(bank: Vec<String>) -> i32 {
+        bank.iter()
+            .map(|s| s.chars().filter(|&c| c == '1').count())
+            .filter(|&i| i > 0)
+            .collect::<Vec<_>>()
+            .windows(2)
+            .map(|x| x[0] * x[1])
+            .sum::<usize>() as _
+    }
+}
+
+// submission codes end
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_2125_example_1() {
+        let bank = vec_string!["011001", "000000", "010100", "001000"];
+
+        let result = 8;
+
+        assert_eq!(Solution::number_of_beams(bank), result);
+    }
+
+    #[test]
+    fn test_2125_example_2() {
+        let bank = vec_string!["000", "111", "000"];
+
+        let result = 0;
+
+        assert_eq!(Solution::number_of_beams(bank), result);
+    }
+}