rs: add «1992. Find All Groups of Farmland»

Signed-off-by: Matej Focko <me@mfocko.xyz>

rs/find-all-groups-of-farmland.rs

@@ -0,0 +1,51 @@
+struct Solution {}
+impl Solution {
+    fn dimensions(grid: &[Vec<i32>]) -> (usize, usize) {
+        (grid.len(), grid[0].len())
+    }
+
+    fn indices(m: usize, n: usize) -> impl Iterator<Item = (usize, usize)> {
+        (0..m).flat_map(move |y| (0..n).map(move |x| (x, y)))
+    }
+
+    fn find(land: &[Vec<i32>], visited: &mut [Vec<bool>], min_x: usize, min_y: usize) -> Vec<i32> {
+        // horizontally
+        let mut max_x = min_x;
+        while max_x < land[min_y].len() && land[min_y][max_x] == 1 {
+            max_y += 1;
+        }
+
+        // vertically
+        let mut max_y = min_y;
+        while max_y < land.len() && land[max_y][min_x] == 1 {
+            max_y += 1;
+        }
+
+        // mark all as visited
+        for (x, y) in (min_y..max_y).flat_map(move |y| (min_x..max_x).map(move |x| (x, y))) {
+            visited[y][x] = true;
+        }
+
+        vec![min_y, min_x, max_y - 1, max_x - 1]
+            .into_iter()
+            .map(|c| c as i32)
+            .collect()
+    }
+
+    pub fn find_farmland(land: Vec<Vec<i32>>) -> Vec<Vec<i32>> {
+        let (m, n) = Self::dimensions(&land);
+
+        let mut farmland: Vec<Vec<i32>> = Vec::new();
+
+        let mut visited = vec![vec![false; n]; m];
+        for (x, y) in Self::indices(m, n) {
+            if land[y][x] == 0 || visited[y][x] {
+                continue;
+            }
+
+            farmland.push(Self::find(&land, &mut visited, x, y));
+        }
+
+        farmland
+    }
+}