A not totally terrible day 19 solution.

inputs/day19

@@ -0,0 +1 @@
+109,424,203,1,21101,0,11,0,1105,1,282,21101,18,0,0,1105,1,259,1202,1,1,221,203,1,21102,1,31,0,1106,0,282,21102,38,1,0,1106,0,259,21002,23,1,2,22102,1,1,3,21102,1,1,1,21102,1,57,0,1105,1,303,2102,1,1,222,20101,0,221,3,21001,221,0,2,21102,259,1,1,21102,1,80,0,1106,0,225,21102,62,1,2,21101,91,0,0,1105,1,303,2101,0,1,223,21001,222,0,4,21101,0,259,3,21101,0,225,2,21101,0,225,1,21101,0,118,0,1105,1,225,20102,1,222,3,21101,94,0,2,21102,133,1,0,1105,1,303,21202,1,-1,1,22001,223,1,1,21101,0,148,0,1105,1,259,1202,1,1,223,20101,0,221,4,21001,222,0,3,21102,17,1,2,1001,132,-2,224,1002,224,2,224,1001,224,3,224,1002,132,-1,132,1,224,132,224,21001,224,1,1,21101,195,0,0,105,1,109,20207,1,223,2,20101,0,23,1,21102,-1,1,3,21101,214,0,0,1106,0,303,22101,1,1,1,204,1,99,0,0,0,0,109,5,2101,0,-4,249,22102,1,-3,1,22101,0,-2,2,21201,-1,0,3,21102,1,250,0,1106,0,225,22101,0,1,-4,109,-5,2105,1,0,109,3,22107,0,-2,-1,21202,-1,2,-1,21201,-1,-1,-1,22202,-1,-2,-2,109,-3,2106,0,0,109,3,21207,-2,0,-1,1206,-1,294,104,0,99,22101,0,-2,-2,109,-3,2106,0,0,109,5,22207,-3,-4,-1,1206,-1,346,22201,-4,-3,-4,21202,-3,-1,-1,22201,-4,-1,2,21202,2,-1,-1,22201,-4,-1,1,21201,-2,0,3,21101,343,0,0,1106,0,303,1105,1,415,22207,-2,-3,-1,1206,-1,387,22201,-3,-2,-3,21202,-2,-1,-1,22201,-3,-1,3,21202,3,-1,-1,22201,-3,-1,2,22102,1,-4,1,21102,384,1,0,1105,1,303,1105,1,415,21202,-4,-1,-4,22201,-4,-3,-4,22202,-3,-2,-2,22202,-2,-4,-4,22202,-3,-2,-3,21202,-4,-1,-2,22201,-3,-2,1,21201,1,0,-4,109,-5,2105,1,0

src/main.rs

@@ -10,6 +10,7 @@ mod repair;
 mod robot;
 #[cfg(test)]
 mod scaffold;
+mod tractor;
 mod wiremap;
 
 use crate::args::Command;

src/tractor.rs

@@ -0,0 +1,134 @@
+use crate::endchannel::channel;
+use crate::machine::Computer;
+use std::thread;
+
+struct TractorMap {
+    base_computer: Computer,
+    data: Vec<bool>,
+    width: usize,
+    affected_size: usize,
+}
+
+impl TractorMap {
+    fn new(file: &str, side_size: usize) -> TractorMap {
+        let     base_computer = Computer::load(file, 0);
+        let mut result = Vec::with_capacity(side_size * side_size);
+        let mut affected = 0;
+
+        result.resize(side_size * side_size, false);
+        for x in 0..side_size {
+            for y in 0..side_size {
+                let mut computer = base_computer.clone();
+                let (    mysend, mut corecv) = channel();
+                let (mut cosend, mut myrecv) = channel();
+
+                mysend.send(x as i64);
+                mysend.send(y as i64);
+                computer.run(&mut corecv, &mut cosend);
+                match myrecv.recv() {
+                    None => panic!("Uh-oh, computer broken!"),
+                    Some(0) => {}
+                    Some(1) => {
+                        affected += 1;
+                        let idx = (y * side_size) + x;
+                        result[idx] = true;
+                    }
+                    Some(x) => panic!("Weird value {}", x),
+                }
+            }
+        }
+
+        TractorMap {
+            base_computer,
+            data: result,
+            width: side_size,
+            affected_size: affected,
+        }
+    }
+
+    fn ask(&self, x: usize, y: usize) -> bool {
+        let mut computer = self.base_computer.clone();
+        let (    mysend, mut corecv) = channel();
+        let (mut cosend, mut myrecv) = channel();
+
+        mysend.send(x as i64);
+        mysend.send(y as i64);
+        computer.run(&mut corecv, &mut cosend);
+        match myrecv.recv() {
+            None => panic!("Uh-oh, computer broken!"),
+            Some(0) => false,
+            Some(1) => true,
+            Some(x) => panic!("Weird value {}", x),
+        }
+    }
+
+    fn find_block(&self, start: (usize, usize), side_size: usize) -> Option<(usize, usize)> {
+        let mut xl = start.0;
+        let mut yl = start.1;
+
+        loop {
+            let mut reset_x = 0;
+
+            loop {
+                if self.ask(xl, yl) {
+                    if reset_x == 0 {
+                        reset_x = xl;
+                    }
+
+                    let xr = xl + side_size - 1;
+                    let yr = yl + side_size - 1;
+
+                    if self.ask(xl, yr) && self.ask(xr, yl) && self.ask(xr, yr) {
+                        return Some((xl, yl));
+                    }
+
+                    xl += 1;
+                } else {
+                    if reset_x != 0 {
+                        break;
+                    } else {
+                        xl += 1;
+                    }
+                }
+            }
+
+            xl = reset_x;
+            yl += 1;
+        }
+    }
+
+    fn print(&self) {
+        for y in 0..self.width {
+            for x in 0..self.width {
+                // if ((x >= 20) && (x <= 22)) && ((y >= 16) && (y <= 18)) {
+                //     assert!(self.data[ (y * self.width) + x ]);
+                //     print!("X");
+                //     continue;
+                // }
+                if self.data[ (y * self.width) + x ] {
+                    print!("#");
+                } else {
+                    print!(".");
+                }
+            }
+            println!();
+        }
+    }
+}
+
+#[test]
+fn day19a() {
+    let tmap = TractorMap::new("inputs/day19", 50);
+    assert_eq!(223, tmap.affected_size);
+    tmap.print();
+    assert_eq!(Some((20, 16)), tmap.find_block((0, 6), 3));
+}
+
+#[test]
+fn day19b() {
+    let tmap = TractorMap::new("inputs/day19", 50);
+    let (x, y) = tmap.find_block((10, 16), 100).expect("a solution");
+    assert_eq!(948, x);
+    assert_eq!(761, y);
+    assert_eq!(9480761, (x * 10000) + y);
+}