solution accepted

.gitignore

@@ -1 +1,2 @@
 */target/
+*/Cargo.lock

spiral_matrix/Cargo.lock

@@ -0,0 +1,7 @@
+# This file is automatically @generated by Cargo.
+# It is not intended for manual editing.
+version = 3
+
+[[package]]
+name = "spiral_matrix"
+version = "0.1.0"

where_will_the_ball_fall/Cargo.toml

@@ -0,0 +1,8 @@
+[package]
+name = "where_will_the_ball_fall"
+version = "0.1.0"
+edition = "2021"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]

where_will_the_ball_fall/src/main.rs

@@ -0,0 +1,59 @@
+fn find_ball(grid: Vec<Vec<i32>>) -> Vec<i32> {
+    let balls = grid[0].len();
+    let mut res = vec![-1; balls];
+
+    for ball in 0..balls {
+        let mut pos = ball;
+        let mut stuck = false;
+        for row in grid.iter() {
+            if let Some(npos) = can_fall(pos, row) {
+                pos = npos as usize;
+            } else {
+                stuck = true;
+                break;
+            }
+        }
+        if !stuck {
+            res[ball] = pos as i32;
+        }
+    }
+
+    res
+}
+
+fn can_fall(pos: usize, row: &[i32]) -> Option<i32> {
+    //
+    let mut res = None;
+    let len = row.len();
+    match row[pos] {
+        1 => {
+            if pos < len.saturating_sub(1) {
+                let right = row[pos + 1];
+                if right > 0 {
+                    res = Some(pos as i32 + 1);
+                }
+            }
+        }
+        _ => {
+            if pos > 0 {
+                let left = row[pos - 1];
+                if left < 0 {
+                    res = Some(pos as i32 - 1);
+                }
+            }
+        }
+    }
+    res
+}
+
+fn main() {
+    let res = find_ball(vec![
+        vec![1, 1, 1, -1, -1],
+        vec![1, 1, 1, -1, -1],
+        vec![-1, -1, -1, 1, 1],
+        vec![1, 1, 1, 1, -1],
+        vec![-1, -1, -1, -1, -1],
+    ]);
+
+    dbg!(res);
+}