From 582b512e28ef8779893a1716fcf4c1da5d7f63fe Mon Sep 17 00:00:00 2001
From: Gleb Koval <gleb@koval.net>
Date: Sat, 4 Jun 2022 23:47:01 +0100
Subject: [PATCH] n-queens

---
 n-queens/sol.rs | 49 +++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 49 insertions(+)
 create mode 100644 n-queens/sol.rs

diff --git a/n-queens/sol.rs b/n-queens/sol.rs
new file mode 100644
index 0000000..15b499a
--- /dev/null
+++ b/n-queens/sol.rs
@@ -0,0 +1,49 @@
+// TODO : Tidy up?? This is quite the unreadable mess at the moment
+impl Solution {
+    pub fn search(board: Vec<Vec<i32>>) -> Vec<Vec<i32>> {
+        if board.len() == 1 {
+            return board[0].iter()
+                .map(|n| vec![*n])
+                .collect();
+        }
+        board[0].iter()
+            .map(|&current|
+                Solution::search(
+                    board[1..].iter()
+                        .enumerate()
+                        .map(|(idx, row)| {
+                            row.iter()
+                                .filter_map(|n| if *n != current &&
+                                    *n != current - idx as i32 - 1 &&
+                                    *n != current + idx as i32 + 1 {
+                                    Some(*n)
+                                } else { None })
+                                .collect()
+                        })
+                        .collect()
+                )
+                .into_iter()
+                .map(|mut row| {
+                    row.insert(0, current);
+                    row
+                })
+                .collect::<Vec<Vec<i32>>>()
+            )
+            .flatten()
+            .collect()
+    }
+    pub fn solve_n_queens(n: i32) -> Vec<Vec<String>> {
+        Solution::search(vec![(0..n).collect(); n as usize])
+            .into_iter()
+            .map(|solution| solution.into_iter()
+                .map(|position| {
+                    let mut converted = ".".repeat(position as usize);
+                    converted.push('Q');
+                    converted.push_str(".".repeat(n as usize - position as usize - 1).as_str());
+                    converted
+                })
+                .collect()
+            )
+            .collect()
+    }
+}
\ No newline at end of file