Merge pull request #1541 from cezarbbb/Backtracking09

添加 0051.N皇后 Rust版本

problems/0051.N皇后.md

@@ -558,6 +558,56 @@ func solveNQueens(_ n: Int) -> [[String]] {
 }
 ```
 
+### Rust
+
+```Rust
+impl Solution {
+    fn is_valid(row: usize, col: usize, chessboard: &mut Vec<Vec<char>>, n: usize) -> bool {
+        let mut i = 0 as usize;
+        while i < row { 
+            if chessboard[i][col] == 'Q' { return false; }
+            i += 1;
+        }
+        let (mut i, mut j) = (row as i32 - 1, col as i32 - 1);
+        while i >= 0 && j >= 0 {
+            if chessboard[i as usize][j as usize] == 'Q' { return false; }
+            i -= 1;
+            j -= 1;
+        }
+        let (mut i, mut j) = (row as i32 - 1, col as i32 + 1);
+        while i >= 0 && j < n as i32 {
+            if chessboard[i as usize][j as usize] == 'Q' { return false; }
+            i -= 1;
+            j += 1;
+        }
+        return true;
+    }
+    fn backtracking(result: &mut Vec<Vec<String>>, n: usize, row: usize, chessboard: &mut Vec<Vec<char>>) {
+        if row == n {
+            let mut chessboard_clone: Vec<String> = Vec::new();
+            for i in chessboard {
+                chessboard_clone.push(i.iter().collect::<String>());
+            }
+            result.push(chessboard_clone);
+            return;
+        }
+        for col in 0..n {
+            if Self::is_valid(row, col, chessboard, n) {
+                chessboard[row][col] = 'Q';
+                Self::backtracking(result, n, row + 1, chessboard);
+                chessboard[row][col] = '.';
+            }
+        }
+    }
+    pub fn solve_n_queens(n: i32) -> Vec<Vec<String>> {
+        let mut result: Vec<Vec<String>> = Vec::new();
+        let mut chessboard: Vec<Vec<char>> = vec![vec!['.'; n as usize]; n as usize];
+        Self::backtracking(&mut result, n as usize, 0, &mut chessboard);
+        result
+    }
+}
+```
+
 ### C
 ```c
 char ***ans;