20250215 finished.

src/problem/mod.rs

@@ -486,3 +486,5 @@ mod p1760_minimum_limit_of_balls_in_a_bag;
 mod p1742_maximum_number_of_balls_in_a_box;
 
 mod p1552_magnetic_force_between_two_balls;
+
+mod p1706_where_will_the_ball_fall;

src/problem/p1706_where_will_the_ball_fall.rs

@@ -0,0 +1,115 @@
+/**
+ * [1706] Where Will the Ball Fall
+ */
+pub struct Solution {}
+
+// submission codes start here
+use std::collections::HashMap;
+
+const LEFT: i32 = -1;
+const RIGHT: i32 = 1;
+
+struct Grid {
+    m: usize,
+    n: usize,
+    grid: Vec<Vec<i32>>,
+    memory: HashMap<usize, HashMap<usize, Option<usize>>>,
+}
+
+impl Grid {
+    fn new(grid: Vec<Vec<i32>>) -> Self {
+        let m = grid.len();
+        let n = grid[0].len();
+
+        let mut memory = HashMap::new();
+
+        // 如果可能到达m行
+        // 就已经掉出去了
+        let row = memory.entry(m).or_insert(HashMap::new());
+        for i in 0..n {
+            row.insert(i, Some(i));
+        }
+
+        Self { m, n, grid, memory }
+    }
+
+    fn search(&mut self, x: usize, y: usize) -> Option<usize> {
+        if let Some(result) = self
+            .memory
+            .get(&x)
+            .into_iter()
+            .filter_map(|x| x.get(&y))
+            .next()
+        {
+            return result.as_ref().map(|x| *x);
+        }
+
+        let result = if self.grid[x][y] == LEFT {
+            // 挡板朝向左边
+            if y > 0 {
+                if self.grid[x][y - 1] == RIGHT {
+                    None
+                } else {
+                    self.search(x + 1, y - 1)
+                }
+            } else {
+                None
+            }
+        } else {
+            // 挡板朝向右边
+            if y < self.n - 1 {
+                if self.grid[x][y + 1] == LEFT {
+                    None
+                } else {
+                    self.search(x + 1, y + 1)
+                }
+            } else {
+                None
+            }
+        };
+
+        let row = self.memory.entry(x).or_insert(HashMap::new());
+        row.insert(y, result.clone());
+
+        result
+    }
+}
+
+impl Solution {
+    pub fn find_ball(grid: Vec<Vec<i32>>) -> Vec<i32> {
+        let mut grid = Grid::new(grid);
+
+        let mut result = Vec::with_capacity(grid.n);
+
+        for i in 0..grid.n {
+            result.push(if let Some(pos) = grid.search(0, i) {
+                pos as i32
+            } else {
+                -1
+            });
+        }
+
+        result
+    }
+}
+
+// submission codes end
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_1706() {
+        assert_eq!(
+            vec![1, -1, -1, -1, -1],
+            Solution::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]
+            ])
+        );
+    }
+}