alokmenghrajani
diff --git a/‎src/main.rs
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+1Lines changed: 1 addition & 0 deletions b/‎src/main.rs
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+1Lines changed: 1 addition & 0 deletions
diff --git a/‎src/year_2017/day14.rs
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-2Lines changed: 0 additions & 2 deletions b/‎src/year_2017/day14.rs
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-2Lines changed: 0 additions & 2 deletions
diff --git a/‎src/year_2017/day16.rs
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+1Lines changed: 1 addition & 0 deletions b/‎src/year_2017/day16.rs
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+1Lines changed: 1 addition & 0 deletions
diff --git a/‎src/year_2017/day17.rs
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+39Lines changed: 39 additions & 0 deletions b/‎src/year_2017/day17.rs
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+39Lines changed: 39 additions & 0 deletions
diff --git a/‎src/year_2017/mod.rs
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@@ -83,6 +83,7 @@ fn main() {
         (2017, 14) => year_2017::day14::run("wenycdww"),
         (2017, 15) => year_2017::day15::run(591, 393),
         (2017, 16) => year_2017::day16::run(&inputs::read_first_line(year, day)),
+        (2017, 17) => year_2017::day17::run(354),
 
         // Other
         (_, _) => panic!("Not implemented :("),
 
@@ -19,8 +19,6 @@ pub fn run(input: &str) {
 fn solve_part1(input: &str) -> usize {
     // convert the input into a grid
     let grid = build_grid(input);
-    let mut used = 0;
-
     return grid.len();
 }
 
 
@@ -40,6 +40,7 @@ fn solve_part2(input: &[u8], iter: usize) -> Vec<u8> {
     return b;
 }
 
+#[allow(non_snake_case)]
 fn transform(moves: String, state: &[u8]) -> Vec<u8> {
     let L = state.len();
     let mut r = Vec::new();
 
@@ -0,0 +1,39 @@
+pub fn run(step: usize) {
+    let part1 = solve_part1(step);
+    println!("part 1: {}", part1);
+    assert_eq!(part1, 2000);
+
+    let part2 = solve_part2(step);
+    println!("part 2: {}", part2);
+    assert_eq!(part2, 10242889);
+}
+
+fn solve_part1(step: usize) -> usize {
+    // I wasn't able to find a way to re-use code between part1 and part2.
+    // For part1, we use a buffer.
+    let mut buf = Vec::new();
+    buf.push(0);
+    let mut pos = 0;
+    for i in 1..2018 {
+        pos = (pos + step) % i;
+        buf.insert(pos, i);
+        pos += 1;
+    }
+    pos = pos % 2017;
+    return buf[pos];
+}
+
+fn solve_part2(step: usize) -> usize {
+    // 0 is at offset 0. It makes the search easy. We no longer need a buffer, just keep track
+    // of what was the last element to get added right after 0.
+    let mut pos = 0;
+    let mut last = None;
+    for i in 1..(50_000_000 + 1) {
+        pos = (pos + step) % i;
+        if pos == 0 {
+            last = Some(i);
+        }
+        pos += 1;
+    }
+    return last.unwrap();
+}
@@ -14,3 +14,4 @@ pub mod day13;
 pub mod day14;
 pub mod day15;
 pub mod day16;
+pub mod day17;
Original file line number	Diff line number	Diff line change
`@@ -19,8 +19,6 @@ pub fn run(input: &str) {`
`19`	`19`	`fn solve_part1(input: &str) -> usize {`
`20`	`20`	`// convert the input into a grid`
`21`	`21`	`let grid = build_grid(input);`
`22`		`- let mut used = 0;`
`23`		`-`
`24`	`22`	`return grid.len();`
`25`	`23`	`}`
`26`	`24`
Original file line number	Diff line number	Diff line change
`@@ -40,6 +40,7 @@ fn solve_part2(input: &[u8], iter: usize) -> Vec<u8> {`
`40`	`40`	`return b;`
`41`	`41`	`}`
`42`	`42`
	`43`	`+#[allow(non_snake_case)]`
`43`	`44`	`fn transform(moves: String, state: &[u8]) -> Vec<u8> {`
`44`	`45`	`let L = state.len();`
`45`	`46`	`let mut r = Vec::new();`