Add solution for Day 01 of 2016.

2016/day-01/input.txt

@@ -0,0 +1 @@
+R4, R3, L3, L2, L1, R1, L1, R2, R3, L5, L5, R4, L4, R2, R4, L3, R3, L3, R3, R4, R2, L1, R2, L3, L2, L1, R3, R5, L1, L4, R2, L4, R3, R1, R2, L5, R2, L189, R5, L5, R52, R3, L1, R4, R5, R1, R4, L1, L3, R2, L2, L3, R4, R3, L2, L5, R4, R5, L2, R2, L1, L3, R3, L4, R4, R5, L1, L1, R3, L5, L2, R76, R2, R2, L1, L3, R189, L3, L4, L1, L3, R5, R4, L1, R1, L1, L1, R2, L4, R2, L5, L5, L5, R2, L4, L5, R4, R4, R5, L5, R3, L1, L3, L1, L1, L3, L4, R5, L3, R5, R3, R3, L5, L5, R3, R4, L3, R3, R1, R3, R2, R2, L1, R1, L3, L3, L3, L1, R2, L1, R4, R4, L1, L1, R3, R3, R4, R1, L5, L2, R2, R3, R2, L3, R4, L5, R1, R4, R5, R4, L4, R1, L3, R1, R3, L2, L3, R1, L2, R3, L3, L1, L3, R4, L4, L5, R3, R5, R4, R1, L2, R3, R5, L5, L4, L1, L1

2016/day-01/sample.txt

@@ -0,0 +1 @@
+R8, R4, R4, R8

2016/day-01/solution.rs

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+use std::collections::HashSet;
+use std::error::Error;
+use std::env;
+use std::fs::File;
+use std::io::prelude::*;
+use std::path::Path;
+use std::str;
+
+fn dist(pos: (i32, i32)) -> i32 {
+    let (x, y) = pos;
+
+    return x.abs() + y.abs()
+}
+
+fn main() {
+    let args: Vec<String> = env::args().collect();
+    let path = Path::new(&args[1]);
+    let display = path.display();
+
+    // Open the path in read-only mode, returns `io::Result<File>`
+    let mut file = match File::open(&path) {
+        // The `description` method of `io::Error` returns a string that
+        // describes the error
+        Err(why) => panic!("couldn't open {}: {}", display,
+                           why.description()),
+        Ok(file) => file,
+    };
+
+    let mut content = String::new();
+    match file.read_to_string(&mut content) {
+        Err(why) => panic!("couldn't open {}: {}", display,
+                           why.description()),
+        Ok(_) => {},
+    };
+
+    let mut posx = 0;
+    let mut posy = 0;
+    let mut dir = 0;
+    let mut found = false;
+
+    let mut positions = HashSet::new();
+    positions.insert((posx, posy));
+
+    for instruction in content.split(", ") {
+        let turn = &instruction[..1];
+        let steps_opt: Option<i32> = instruction[1..].trim().parse().ok();
+        let steps = match steps_opt {
+            Some(num) => num,
+            None => panic!("Could note parse number of steps"),
+        };
+        if turn == "R" {
+            dir += 1;
+        } else {
+            dir -= 1;
+        }
+        dir = (dir + 4) % 4;
+
+        let backwards = if dir & 2 == 2 { -1 } else { 1 };
+        if dir & 1 == 1 {
+            // Move in y direction
+            for y in 1..(steps + 1) {
+                if positions.contains(&(posx, posy + y * backwards)) && !found {
+                    found = true;
+                    println!("Arrived at the same position, dist {}", dist((posx, posy + y * backwards)));
+                } else {
+                    positions.insert((posx, posy + y * backwards));
+                }
+            }
+            posy += steps * backwards;
+        } else {
+            // Move in x direction
+            for x in 1..(steps + 1) {
+                if positions.contains(&(posx + x * backwards, posy)) && !found {
+                    println!("Arrived at the same position, dist {}", dist((posx + x * backwards, posy)));
+                    found = true;
+                } else {
+                    positions.insert((posx + x * backwards, posy));
+                }
+            }
+            posx += steps * backwards;
+        }
+    }
+
+    println!("Total distance is {}", dist((posx, posy)))
+
+}