rs: add «85. Maximal Rectangle»

Signed-off-by: Matej Focko <mfocko@redhat.com>

rs/maximal-rectangle.rs

@@ -0,0 +1,40 @@
+use std::cmp;
+
+impl Solution {
+    fn indices(rows: usize, cols: usize) -> impl Iterator<Item = (usize, usize)> {
+        (0..rows * cols).map(move |i| (i / cols, i % cols))
+    }
+
+    fn get(dp: &[Vec<(usize, usize)>], y: usize, x: usize) -> (usize, usize) {
+        if y > dp.len() || x > dp[y].len() {
+            return (0, 0);
+        }
+
+        dp[y][x]
+    }
+
+    pub fn maximal_rectangle(matrix: Vec<Vec<char>>) -> i32 {
+        let mut found_max = 0;
+        let mut dp = vec![vec![(0, 0); matrix[0].len()]; matrix.len()];
+
+        for (y, x) in Self::indices(matrix.len(), matrix[0].len()) {
+            if matrix[y][x] != '1' {
+                continue;
+            }
+
+            let width = 1 + Self::get(&dp, y, x - 1).0;
+            let height = 1 + Self::get(&dp, y - 1, x).1;
+            dp[y][x] = (width, height);
+
+            found_max = cmp::max(found_max, cmp::max(width, height));
+
+            let mut min_width = width;
+            for yy in ((y - height + 1)..y).rev() {
+                min_width = cmp::min(min_width, dp[yy][x].0);
+                found_max = cmp::max(found_max, min_width * (y - yy + 1));
+            }
+        }
+
+        found_max.try_into().unwrap()
+    }
+}