LC 1572. Matrix Diagonal Sum (Rust)

Author: raul-sauco

README.md

@@ -425,6 +425,7 @@ Solutions to LeetCode problems. The first column links to the problem in LeetCod
 | [1523. Count Odd Numbers in an Interval Range][lc1523]                                        | 🟢 Easy    | [![python](res/py.png)][lc1523py] [![rust](res/rs.png)][lc1523rs]                                     |
 | [1539. Kth Missing Positive Number][lc1539]                                                   | 🟢 Easy    | [![python](res/py.png)][lc1539py] [![rust](res/rs.png)][lc1539rs]                                     |
 | [1544. Make The String Great][lc1544]                                                         | 🟢 Easy    | [![python](res/py.png)][lc1544py]                                                                     |
+| [1572. Matrix Diagonal Sum][lc1572]                                                           | 🟢 Easy    | [![rust](res/rs.png)][lc1572rs]                                                                       |
 | [1578. Minimum Time to Make Rope Colorful][lc1578]                                            | 🟠 Medium  | [![python](res/py.png)][lc1578py]                                                                     |
 | [1579. Remove Max Number of Edges to Keep Graph Fully Traversable][lc1579]                    | 🔴 Hard    | [![python](res/py.png)][lc1579py]                                                                     |
 | [1584. Min Cost to Connect All Points][lc1584]                                                | 🟠 Medium  | [![python](res/py.png)][lc1584py]                                                                     |
@@ -1407,6 +1408,8 @@ Solutions to LeetCode problems. The first column links to the problem in LeetCod
 [lc1539rs]: leetcode/kth-missing-positive-number.rs
 [lc1544]: https://leetcode.com/problems/make-the-string-great/
 [lc1544py]: leetcode/make-the-string-great.py
+[lc1572]: https://leetcode.com/problems/matrix-diagonal-sum/
+[lc1572rs]: leetcode/matrix-diagonal-sum.rs
 [lc1578]: https://leetcode.com/problems/minimum-time-to-make-rope-colorful/
 [lc1578py]: leetcode/minimum-time-to-make-rope-colorful.py
 [lc1579]: https://leetcode.com/problems/remove-max-number-of-edges-to-keep-graph-fully-traversable/

leetcode/matrix-diagonal-sum.rs

@@ -0,0 +1,54 @@
+// 1572. Matrix Diagonal Sum
+// 🟢 Easy
+//
+// https://leetcode.com/problems/matrix-diagonal-sum/
+//
+// Tags: Array - Matrix
+
+struct Solution;
+impl Solution {
+    /// A cell belongs to a diagonal if it fulfills either of two conditions,
+    /// r == c => main positive diagonal or r+c == n-1 => main negative
+    /// diagonal. We iterate over all cells, if it matches, we add its value to
+    /// the result.
+    ///
+    /// Time complexity: O(n^2) - We iterate over all cells, for each, we check
+    /// if it matches the conditions and, if it does, add it to the result.
+    /// Space complexity: O(1) - We only store integer values and pointers.
+    ///
+    /// Runtime 0 ms Beats 100%
+    /// Memory 2.2 MB Beats 85.71%
+    pub fn diagonal_sum(mat: Vec<Vec<i32>>) -> i32 {
+        let n = mat.len();
+        let mut res = 0;
+        // Iterate over all cells checking if the cell belongs to a diagonal.
+        for r in 0..n {
+            for c in 0..n {
+                if r == c || r + c == n - 1 {
+                    res += mat[r][c];
+                }
+            }
+        }
+        res
+    }
+}
+
+// Tests.
+fn main() {
+    let tests = [
+        (vec![vec![1, 2, 3], vec![4, 5, 6], vec![7, 8, 9]], 25),
+        (
+            vec![
+                vec![1, 1, 1, 1],
+                vec![1, 1, 1, 1],
+                vec![1, 1, 1, 1],
+                vec![1, 1, 1, 1],
+            ],
+            8,
+        ),
+    ];
+    for t in tests {
+        assert_eq!(Solution::diagonal_sum(t.0), t.1);
+    }
+    println!("\x1b[92m» All tests passed!\x1b[0m")
+}