From cd1b2b071d91d952a3be16ad1f4591155b5d02fc Mon Sep 17 00:00:00 2001
From: SquidSpirit <squid@squidspirit.com>
Date: Sun, 17 Aug 2025 01:43:02 +0800
Subject: [PATCH] feat: add initial implementation of unique paths III solution

---
 980_unique_path_3/Cargo.lock  |  7 +++
 980_unique_path_3/Cargo.toml  |  6 +++
 980_unique_path_3/src/main.rs | 95 +++++++++++++++++++++++++++++++++++
 3 files changed, 108 insertions(+)
 create mode 100644 980_unique_path_3/Cargo.lock
 create mode 100644 980_unique_path_3/Cargo.toml
 create mode 100644 980_unique_path_3/src/main.rs

diff --git a/980_unique_path_3/Cargo.lock b/980_unique_path_3/Cargo.lock
new file mode 100644
index 0000000..bf2a768
--- /dev/null
+++ b/980_unique_path_3/Cargo.lock
@@ -0,0 +1,7 @@
+# This file is automatically @generated by Cargo.
+# It is not intended for manual editing.
+version = 4
+
+[[package]]
+name = "unique_path_3"
+version = "0.1.0"
diff --git a/980_unique_path_3/Cargo.toml b/980_unique_path_3/Cargo.toml
new file mode 100644
index 0000000..7314b41
--- /dev/null
+++ b/980_unique_path_3/Cargo.toml
@@ -0,0 +1,6 @@
+[package]
+name = "unique_path_3"
+version = "0.1.0"
+edition = "2024"
+
+[dependencies]
diff --git a/980_unique_path_3/src/main.rs b/980_unique_path_3/src/main.rs
new file mode 100644
index 0000000..c6b1db8
--- /dev/null
+++ b/980_unique_path_3/src/main.rs
@@ -0,0 +1,95 @@
+fn main() {
+    println!(
+        "{}",
+        Solution::unique_paths_iii(vec![vec![1, 0, 0, 0], vec![0, 0, 0, 0], vec![0, 0, 2, -1]])
+    );
+}
+
+struct Solution;
+
+impl Solution {
+    pub fn unique_paths_iii(grid: Vec<Vec<i32>>) -> i32 {
+        let m = grid.len();
+        let n = grid.first().unwrap().len();
+
+        let mut initial_visited: Vec<Vec<bool>> =
+            vec![vec![false; grid.first().unwrap().len()]; grid.len()];
+
+        let mut start_point: (i32, i32) = (0, 0);
+        let mut end_point: (i32, i32) = (0, 0);
+        let mut left_blocks = (m * n) as i32;
+        for (i, inner_vec) in grid.iter().enumerate() {
+            for (j, &value) in inner_vec.iter().enumerate() {
+                match value {
+                    1 => start_point = (i as i32, j as i32),
+                    2 => end_point = (i as i32, j as i32),
+                    -1 => {
+                        initial_visited[i][j] = true;
+                        left_blocks -= 1;
+                    }
+                    _ => {}
+                }
+            }
+        }
+
+        let mut dfs = DFS {
+            directions: vec![(1, 0), (0, 1), (-1, 0), (0, -1)],
+            end_point: end_point,
+            result: 0,
+        };
+        dfs.run(DFSParams {
+            point: start_point,
+            visited: initial_visited,
+            left_blocks: left_blocks - 1,
+        });
+        dfs.result
+    }
+}
+
+struct DFS {
+    directions: Vec<(i32, i32)>,
+    end_point: (i32, i32),
+    result: i32,
+}
+
+struct DFSParams {
+    point: (i32, i32),
+    visited: Vec<Vec<bool>>,
+    left_blocks: i32,
+}
+
+impl DFS {
+    fn run(&mut self, params: DFSParams) {
+        let mut stack: Vec<DFSParams> = vec![params];
+
+        while !stack.is_empty() {
+            let current = stack.pop().unwrap();
+
+            if current.point.0 < 0
+                || current.point.1 < 0
+                || current.point.0 >= current.visited.len() as i32
+                || current.point.1 >= current.visited.first().unwrap().len() as i32
+                || current.visited[current.point.0 as usize][current.point.1 as usize]
+            {
+                continue;
+            }
+
+            if current.point == self.end_point {
+                if current.left_blocks == 0 {
+                    self.result += 1;
+                }
+            }
+
+            for &direction in &self.directions {
+                let mut new_visited = current.visited.clone();
+                new_visited[current.point.0 as usize][current.point.1 as usize] = true;
+
+                stack.push(DFSParams {
+                    point: (current.point.0 + direction.0, current.point.1 + direction.1),
+                    visited: new_visited,
+                    left_blocks: current.left_blocks - 1,
+                });
+            }
+        }
+    }
+}