Generate random chess position: Difference between revisions

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 ...qB...
 </pre>
+=={{header|Rust}}==
+<lang Rust>use std::fmt::Write;
+use rand::{Rng, distributions::{Distribution, Standard}};
+const EMPTY: u8 = b'.';
+#[derive(Clone, Debug)]
+struct Board {
+    grid: [[u8; 8]; 8],
+}
+impl Distribution<Board> for Standard {
+    fn sample<R: Rng + ?Sized>(&self, rng: &mut R) -> Board {
+        let mut board = Board::empty();
+        board.place_kings(rng);
+        board.place_pieces(rng, b"PPPPPPPP", true);
+        board.place_pieces(rng, b"pppppppp", true);
+        board.place_pieces(rng, b"RNBQBNR", false);
+        board.place_pieces(rng, b"rnbqbnr", false);
+        board
+    }
+}
+impl Board {
+    fn empty() -> Self {
+        Board { grid: [[EMPTY; 8]; 8] }
+    }
+    fn fen(&self) -> String {
+        let mut fen = String::new();
+        let mut count_empty = 0;
+        for row in &self.grid {
+            for &ch in row {
+                print!("{} ", ch as char);
+                if ch == EMPTY {
+                    count_empty += 1;
+                } else {
+                    if count_empty > 0 {
+                        write!(fen, "{}", count_empty).unwrap();
+                        count_empty = 0;
+                    }
+                    fen.push(ch as char);
+                }
+            }
+            if count_empty > 0 {
+                write!(fen, "{}", count_empty).unwrap();
+                count_empty = 0;
+            }
+            fen.push('/');
+            println!();
+        }
+        fen.push_str(" w - - 0 1");
+        fen
+    }
+    fn place_kings<R: Rng + ?Sized>(&mut self, rng: &mut R) {
+        loop {
+            let r1: i8 = rng.gen_range(0, 8);
+            let c1: i8 = rng.gen_range(0, 8);
+            let r2: i8 = rng.gen_range(0, 8);
+            let c2: i8 = rng.gen_range(0, 8);
+            if r1 != r2 && (r1 - r2).abs() > 1 && (c1 - c2).abs() > 1 {
+                self.grid[r1 as usize][c1 as usize] = b'K';
+                self.grid[r2 as usize][c2 as usize] = b'k';
+                return;
+            }
+        }
+    }
+    fn place_pieces<R: Rng + ?Sized>(&mut self, rng: &mut R, pieces: &[u8], is_pawn: bool) {
+        let num_to_place = rng.gen_range(0, pieces.len());
+        for &piece in pieces.iter().take(num_to_place) {
+            let mut r = rng.gen_range(0, 8);
+            let mut c = rng.gen_range(0, 8);
+            while self.grid[r][c] != EMPTY || (is_pawn && (r == 7 || r == 0)) {
+                r = rng.gen_range(0, 8);
+                c = rng.gen_range(0, 8);
+            }
+            self.grid[r][c] = piece;
+        }
+    }
+}
+fn main() {
+    let b: Board = rand::random();
+    println!("{}", b.fen());
+}</lang>
+{{out}}
+<pre>b . . . . . . .
+. R P . . . . .
+n . . P . . . k
+p . . . P r . .
+P p . b . . . n
+. . P . . . . .
+K . . . . . . .
+. . . q . . . .
+b7/1RP5/n2P3k/p3Pr2/Pp1b3n/2P5/K7/3q4/ w - - 0 1</pre>
 =={{header|Scala}}==