1 files changed, 63 insertions, 0 deletions
diff --git a/2017/src/bin/day_10.rs b/2017/src/bin/day_10.rs
new file mode 100644
index 0000000..faec18a
--- /dev/null
+++ b/2017/src/bin/day_10.rs
@@ -0,0 +1,63 @@
+extern crate advent_of_code_2017;
+use advent_of_code_2017::*;
+
+fn main() {
+    let args = AdventArgs::init();
+
+    let lengths: Vec<usize> = if args.part == 1 {
+        args.input[0].split(",").map(|x| x.parse().unwrap()).collect()
+    } else {
+        let suffix: [usize; 5] = [17, 31, 73, 47, 23];
+        args.input[0].as_bytes()
+            .iter().map(|&x| x as usize)
+            .chain(suffix.iter().cloned())
+            .collect()
+    };
+    
+    let mut position = 0;
+    let mut list: Vec<u32> = (0..256).collect();
+
+    if args.part == 1 {
+        hash_round(&mut list, &lengths, &mut position, 0);
+    } else {
+        for i in 0..64 {
+            let skip = lengths.len() * i;
+            hash_round(&mut list, &lengths, &mut position, skip);            
+        }
+    }
+
+
+    if args.part == 1 {
+        let answer = list[0]*list[1];
+        println!("{}", answer);
+    } else {
+        let mut current_char = 0;
+        for (i, l) in list.iter().enumerate() {
+            current_char = current_char ^ l;
+            if i % 16 == 15 {
+                print!("{:02x}", current_char);
+                current_char = 0;
+            }
+        }
+        println!("");
+    }
+}
+
+fn hash_round(list: &mut Vec<u32>, lengths: &Vec<usize>, position: &mut usize, skip: usize) {
+    for (inner_skip, &length) in lengths.iter().enumerate() {
+        reverse(list, *position, length);
+        *position = (*position + length + skip + inner_skip) % list.len();
+    }
+}
+
+fn reverse(list: &mut Vec<u32>, position: usize, length: usize) {
+    let mut a = position;
+    let mut b = position + length - 1;
+    let len = list.len();
+    while a < b {
+        list.swap(a%len, b%len);
+        
+        a += 1;
+        b -= 1;
+    }
+}