From ff04cb1eb02083641c6a960581fe857ef95b6cc2 Mon Sep 17 00:00:00 2001
From: Stefan Plantikow <stefan.plantikow@googlemail.com>
Date: Sun, 20 Nov 2011 01:53:12 +0100
Subject: [PATCH] Added a little sudoku solver to test/bench for everone's
 puzzle solving needs

---
 src/test/bench/sudoku.rs | 170 +++++++++++++++++++++++++++++++++++++++
 1 file changed, 170 insertions(+)
 create mode 100644 src/test/bench/sudoku.rs

diff --git a/src/test/bench/sudoku.rs b/src/test/bench/sudoku.rs
new file mode 100644
index 0000000000000..51338605a820b
--- /dev/null
+++ b/src/test/bench/sudoku.rs
@@ -0,0 +1,170 @@
+use std;
+
+import std::io;
+import std::str;
+import std::uint;
+import std::u8;
+import std::vec;
+import std::bitv;
+
+// Computes a single solution to a given 9x9 sudoku
+//
+// Call with "-" to read input sudoku from stdin
+//
+// The expected line-based format is:
+//
+// 9,9
+// <row>,<column>,<color>
+// ...
+//
+// Row and column are 0-based (i.e. <= 8) and color is 1-based (>=1,<=9).
+// A color of 0 indicates an empty field.
+//
+// If called without arguments, sudoku solves a built-in example sudoku
+//
+
+export grid_t, read_grid, solve_grid, write_grid;
+
+// internal type of sudoku grids
+type grid = [[mutable u8]];
+
+// exported type of sudoku grids
+tag grid_t { grid_ctor(grid); }
+
+// read a sudoku problem from file f
+fn read_grid(f: io::reader) -> grid_t {
+    assert f.read_line() == "9,9"; /* assert first line is exactly "9,9" */
+
+    let g = vec::init_fn({|_i| vec::init_elt_mut(0 as u8, 10u) }, 10u);
+    while !f.eof() {
+        // FIXME: replace with unicode compliant call
+        let comps = str::split(str::trim(f.read_line()), ',' as u8);
+        if vec::len(comps) >= 3u {
+            let row     = uint::from_str(comps[0]) as u8;
+            let col     = uint::from_str(comps[1]) as u8;
+            g[row][col] = uint::from_str(comps[2]) as u8;
+        }
+    }
+    ret grid_ctor(g);
+}
+
+// solve sudoku grid
+fn solve_grid(g: grid_t) {
+    fn next_color(g: grid, row: u8, col: u8, start_color: u8) -> bool {
+        if start_color < 10u8 {
+            // colors not yet used
+            let avail = bitv::create(10u, false);
+            u8::range(start_color, 10u8) { |color|
+                bitv::set(avail, color as uint, true);
+            }
+
+            // drop colors already in use in neighbourhood
+            drop_colors(g, avail, row, col);
+
+            // find first remaining color that is available
+            let i = 1 as uint;
+            while i < (10 as uint) { /* FIXME llvm ctlhd */
+                if bitv::get(avail, i) {
+                    g[row][col] = i as u8;
+                    ret true;
+                }
+                i += 1 as uint; /* else */
+            }
+        }
+        g[row][col] = 0u8;
+        ret false;
+    }
+
+    // find colors available in neighbourhood of (row, col)
+    fn drop_colors(g: grid, avail: bitv::t, row: u8, col: u8) {
+        fn drop_color(g: grid, colors: bitv::t, row: u8, col: u8) {
+            let color = g[row][col];
+            if color != 0u8 { bitv::set(colors, color as uint, false); }
+        }
+
+        let it = bind drop_color(g, avail, _, _);
+
+        u8::range(0u8, 9u8) { |idx|
+            it(idx, col); /* check same column fields */
+            it(row, idx); /* check same row fields */
+        }
+
+        // check same block fields
+        let row0 = (row / 3u8) * 3u8;
+        let col0 = (col / 3u8) * 3u8;
+        u8::range(row0, row0 + 3u8) { |alt_row|
+            u8::range(col0, col0 + 3u8) { |alt_col| it(alt_row, alt_col); }
+        }
+    }
+
+    let work: [(u8, u8)] = []; /* queue of uncolored fields */
+    u8::range(0u8, 9u8) { |row|
+        u8::range(0u8, 9u8) { |col|
+            let color = (*g)[row][col];
+            if color == 0u8 { work += [(row, col)]; }
+        }
+    }
+
+    let ptr = 0u;
+    let end = vec::len(work);
+    while (ptr < end) {
+        let (row, col) = work[ptr];
+        // is there another color to try?
+        if next_color(*g, row, col, (*g)[row][col] + (1 as u8)) {
+            //  yes: advance work list
+            ptr = ptr + 1u;
+        } else {
+            // no: redo this field aft recoloring pred; unless there is none
+            if ptr == 0u { fail "No solution found for this sudoku"; }
+            ptr = ptr - 1u;
+        }
+    }
+}
+
+fn write_grid(f: io::writer, g: grid_t) {
+    u8::range(0u8, 9u8) { |row|
+        f.write_str(#fmt("%u", (*g)[row][0] as uint));
+        u8::range(1u8, 9u8) { |col|
+            f.write_str(#fmt(" %u", (*g)[row][col] as uint));
+        }
+        f.write_char('\n');
+     }
+}
+
+fn main(args: [str]) {
+    let grid = if vec::len(args) == 1u {
+        // FIXME create sudoku inline since nested vec consts dont work yet
+        let g = vec::init_fn({|_i| vec::init_elt_mut(0 as u8, 10u) }, 10u);
+        g[0][1] = 4u8;
+        g[0][3] = 6u8;
+        g[0][7] = 3u8;
+        g[0][8] = 2u8;
+        g[1][2] = 8u8;
+        g[1][4] = 2u8;
+        g[2][0] = 7u8;
+        g[2][3] = 8u8;
+        g[3][3] = 5u8;
+        g[4][1] = 5u8;
+        g[4][5] = 3u8;
+        g[4][6] = 6u8;
+        g[5][0] = 6u8;
+        g[5][1] = 8u8;
+        g[5][7] = 9u8;
+        g[6][1] = 9u8;
+        g[6][2] = 5u8;
+        g[6][5] = 6u8;
+        g[6][7] = 7u8;
+        g[7][4] = 4u8;
+        g[7][7] = 6u8;
+        g[8][0] = 4u8;
+        g[8][5] = 7u8;
+        g[8][6] = 2u8;
+        g[8][8] = 3u8;
+        grid_ctor(g)
+    } else {
+        read_grid(io::stdin())
+    };
+    solve_grid(grid);
+    write_grid(io::stdout(), grid);
+}
+