LC 1975. Maximum Matrix Sum (Rust)

Author: raul-sauco

README.md

@@ -649,6 +649,7 @@ to the solution in this repository.
 | [1964. Find the Longest Valid Obstacle Course at Each Position][lc1964]                       | 🔴 Hard    | [![python](res/py.png)][lc1964py] [![rust](res/rs.png)][lc1964rs]                                     |
 | [1970. Last Day Where You Can Still Cross][lc1970]                                            | 🔴 Hard    | [![rust](res/rs.png)][lc1970rs]                                                                       |
 | [1971. Find if Path Exists in Graph][lc1971]                                                  | 🟢 Easy    | [![python](res/py.png)][lc1971py]                                                                     |
+| [1975. Maximum Matrix Sum][lc1975]                                                            | 🟠 Medium  | [![rust](res/rs.png)][lc1975rs]                                                                       |
 | [1980. Find Unique Binary String][lc1980]                                                     | 🟠 Medium  | [![rust](res/rs.png)][lc1980rs]                                                                       |
 | [1991. Find the Middle Index in Array][lc1991]                                                | 🟢 Easy    | [![python](res/py.png)][lc1991py]                                                                     |
 | [1996. The Number of Weak Characters in the Game][lc1996]                                     | 🟠 Medium  | [![python](res/py.png)][lc1996py]                                                                     |
@@ -2224,6 +2225,8 @@ to the solution in this repository.
 [lc1970rs]: leetcode/last-day-where-you-can-still-cross.rs
 [lc1971]: https://leetcode.com/problems/find-if-path-exists-in-graph/
 [lc1971py]: leetcode/find-if-path-exists-in-graph.py
+[lc1975]: https://leetcode.com/problems/maximum-matrix-sum/
+[lc1975rs]: leetcode/maximum-matrix-sum.rs
 [lc1980]: https://leetcode.com/problems/find-unique-binary-string/
 [lc1980rs]: leetcode/find-unique-binary-string.rs
 [lc1991]: https://leetcode.com/problems/find-the-middle-index-in-array/

leetcode/maximum-matrix-sum.rs

@@ -0,0 +1,66 @@
+// 1975. Maximum Matrix Sum
+// 🟠 Medium
+//
+// https://leetcode.com/problems/maximum-matrix-sum/
+//
+// Tags: Array - Greedy - Matrix
+
+struct Solution;
+impl Solution {
+    /// Visit all values in the matrix keeping track of the number of negative values, the smallest
+    /// absolute value and the total sum of absolute values. We will be able to find a combination
+    /// to flip any two values, that means that, if we have an even number of negative values, we
+    /// will be able to flip them all, otherwise, there will be one value that we will not be able
+    /// to flip, choose the smallest absolute value.
+    ///
+    /// Time complexity: O(m*n) - We visit each value in the matrix and do O(1) work for each.
+    /// Space complexity: O(1) - The iterator accumulator, one bool, two i64s.
+    ///
+    /// Runtime 0 ms Beats 100%
+    /// Memory 3.19 MB Beats 100%
+    pub fn max_matrix_sum(matrix: Vec<Vec<i32>>) -> i64 {
+        match matrix.into_iter().flat_map(|row| row.into_iter()).fold(
+            (true, i64::MAX, 0i64),
+            |acc, x| {
+                let a = x.abs() as i64;
+                (if x < 0 { !acc.0 } else { acc.0 }, acc.1.min(a), acc.2 + a)
+            },
+        ) {
+            (true, _, total) => total,
+            (false, smallest, total) => total - 2 * smallest,
+        }
+    }
+}
+
+// Tests.
+fn main() {
+    let tests = [
+        (vec![vec![1, -1], vec![-1, 1]], 4),
+        (vec![vec![1, 2, 3], vec![-1, -2, -3], vec![1, 2, 3]], 16),
+    ];
+    println!("\n\x1b[92m» Running {} tests...\x1b[0m", tests.len());
+    let mut success = 0;
+    for (i, t) in tests.iter().enumerate() {
+        let res = Solution::max_matrix_sum(t.0.clone());
+        if res == t.1 {
+            success += 1;
+            println!("\x1b[92m✔\x1b[95m Test {} passed!\x1b[0m", i);
+        } else {
+            println!(
+                "\x1b[31mx\x1b[95m Test {} failed expected: {:?} but got {}!!\x1b[0m",
+                i, t.1, res
+            );
+        }
+    }
+    println!();
+    if success == tests.len() {
+        println!("\x1b[30;42m✔ All tests passed!\x1b[0m")
+    } else if success == 0 {
+        println!("\x1b[31mx \x1b[41;37mAll tests failed!\x1b[0m")
+    } else {
+        println!(
+            "\x1b[31mx\x1b[95m {} tests failed!\x1b[0m",
+            tests.len() - success
+        )
+    }
+}