March 2014 update

Task/N-queens-problem/D/n-queens-problem-3.d

@@ -1,5 +1,3 @@
-import std.stdio, std.conv;
-
 ulong nQueens(in uint nn) pure nothrow
 in {
     assert(nn > 0 && nn <= 27,
@@ -85,6 +83,8 @@ in {
 }
 
 void main(in string[] args) {
+    import std.stdio, std.conv;
+
     immutable uint side = (args.length >= 2) ? args[1].to!uint : 8;
     writefln("N-queens(%d) = %d solutions.", side, side.nQueens);
 }

Task/N-queens-problem/Rust/n-queens-problem.rust

@@ -0,0 +1,44 @@
+// rustc 0.10-pre, 24th Feb
+static side: i8 = 8;
+static queens: i8 = 8; //change side and queens to modify parameters
+
+fn place(mut board: [i8,..side*side], ix:i8) -> Option<[i8,..side*side]> {
+    if board[ix] == 0 {
+        return None
+    };
+    board[ix] = -1;
+    let i1 = ix/side;
+    let j1 = ix % side;
+    for k in range(1,side) {
+        let mut loc :i8 = i1 * side + k;
+        board[loc] = 0;
+        loc = k * side + j1;
+        board[loc] = 0;
+        loc = (i1-k) * side + (j1-k);
+        if loc / side == i1 -k && loc % side == j1 - k && loc != ix && loc >= 0 { board[loc] = 0 };
+        loc = loc + 2 * k;
+        if loc / side == i1 - k && loc % side == j1 + k && loc != ix && loc >= 0 { board[loc] = 0};
+        loc = loc + 2 * side * k;
+        if loc / side == i1 + k && loc % side == j1 + k && loc != ix && loc < side*side { board[loc] = 0};
+        loc = loc - 2 * k;
+        if loc / side == i1 + k && loc % side == j1 - k && loc != ix && loc < side*side { board[loc] = 0};
+    }
+    Some(board)
+}
+
+fn tryplace(b : [i8,..side*side],ix:i8, nq: i8, mut score: u32) -> u32 {
+    if nq == queens { return score + 1 }
+    for ind in range(ix, side*side) {
+        score = match place(b, ind) {
+            Some(b2) => tryplace(b2, ind+1, nq+1, score),
+            None() => score
+        };
+    }
+    return score
+}
+
+fn main() {
+    let b : [i8, ..side*side] = [1,..side*side];
+    let score = tryplace(b, 0, 0, 0);
+    println!("{}", score)
+}