Implement day 21.

2018/benches/days.rs

@@ -72,8 +72,10 @@ day_bench!(day17, 17);
 day_bench!(day18, 18);
 day_bench!(day19, 19);
 day_bench!(day20, 20);
+day_bench!(day21, 21);
 
 benchmark_main!(day01, day02, day03, day04, day05,
                 day06, day07, day08, day09, day10,
                 day11, day12, day13, day14, day15,
-                day16, day17, day18, day19, day20);
+                day16, day17, day18, day19, day20,
+                day21);

2018/loc.svg

@@ -32,10 +32,10 @@ z
       <defs>
        <path d="M 0 0 
 L 0 3.5 
-" id="me1cf09a1d9" style="stroke:#000000;stroke-width:0.8;"/>
+" id="mec9193305a" style="stroke:#000000;stroke-width:0.8;"/>
       </defs>
       <g>
-       <use style="stroke:#000000;stroke-width:0.8;" x="60.305455" xlink:href="#me1cf09a1d9" y="307.584"/>
+       <use style="stroke:#000000;stroke-width:0.8;" x="60.305455" xlink:href="#mec9193305a" y="307.584"/>
       </g>
      </g>
      <g id="text_1">
@@ -71,7 +71,7 @@ z
     <g id="xtick_2">
      <g id="line2d_2">
       <g>
-       <use style="stroke:#000000;stroke-width:0.8;" x="127.941818" xlink:href="#me1cf09a1d9" y="307.584"/>
+       <use style="stroke:#000000;stroke-width:0.8;" x="127.941818" xlink:href="#mec9193305a" y="307.584"/>
       </g>
      </g>
      <g id="text_2">
@@ -110,7 +110,7 @@ z
     <g id="xtick_3">
      <g id="line2d_3">
       <g>
-       <use style="stroke:#000000;stroke-width:0.8;" x="195.578182" xlink:href="#me1cf09a1d9" y="307.584"/>
+       <use style="stroke:#000000;stroke-width:0.8;" x="195.578182" xlink:href="#mec9193305a" y="307.584"/>
       </g>
      </g>
      <g id="text_3">
@@ -139,7 +139,7 @@ z
     <g id="xtick_4">
      <g id="line2d_4">
       <g>
-       <use style="stroke:#000000;stroke-width:0.8;" x="263.214545" xlink:href="#me1cf09a1d9" y="307.584"/>
+       <use style="stroke:#000000;stroke-width:0.8;" x="263.214545" xlink:href="#mec9193305a" y="307.584"/>
       </g>
      </g>
      <g id="text_4">
@@ -153,7 +153,7 @@ z
     <g id="xtick_5">
      <g id="line2d_5">
       <g>
-       <use style="stroke:#000000;stroke-width:0.8;" x="330.850909" xlink:href="#me1cf09a1d9" y="307.584"/>
+       <use style="stroke:#000000;stroke-width:0.8;" x="330.850909" xlink:href="#mec9193305a" y="307.584"/>
       </g>
      </g>
      <g id="text_5">
@@ -193,7 +193,7 @@ z
     <g id="xtick_6">
      <g id="line2d_6">
       <g>
-       <use style="stroke:#000000;stroke-width:0.8;" x="398.487273" xlink:href="#me1cf09a1d9" y="307.584"/>
+       <use style="stroke:#000000;stroke-width:0.8;" x="398.487273" xlink:href="#mec9193305a" y="307.584"/>
       </g>
      </g>
      <g id="text_6">
@@ -286,10 +286,10 @@ z
       <defs>
        <path d="M 0 0 
 L -3.5 0 
-" id="m480ecff4e3" style="stroke:#000000;stroke-width:0.8;"/>
+" id="mcf4dca2140" style="stroke:#000000;stroke-width:0.8;"/>
       </defs>
       <g>
-       <use style="stroke:#000000;stroke-width:0.8;" x="57.6" xlink:href="#m480ecff4e3" y="295.488"/>
+       <use style="stroke:#000000;stroke-width:0.8;" x="57.6" xlink:href="#mcf4dca2140" y="295.488"/>
       </g>
      </g>
      <g id="text_8">
@@ -302,7 +302,7 @@ L -3.5 0
     <g id="ytick_2">
      <g id="line2d_8">
       <g>
-       <use style="stroke:#000000;stroke-width:0.8;" x="57.6" xlink:href="#m480ecff4e3" y="247.488"/>
+       <use style="stroke:#000000;stroke-width:0.8;" x="57.6" xlink:href="#mcf4dca2140" y="247.488"/>
       </g>
      </g>
      <g id="text_9">
@@ -316,7 +316,7 @@ L -3.5 0
     <g id="ytick_3">
      <g id="line2d_9">
       <g>
-       <use style="stroke:#000000;stroke-width:0.8;" x="57.6" xlink:href="#m480ecff4e3" y="199.488"/>
+       <use style="stroke:#000000;stroke-width:0.8;" x="57.6" xlink:href="#mcf4dca2140" y="199.488"/>
       </g>
      </g>
      <g id="text_10">
@@ -331,7 +331,7 @@ L -3.5 0
     <g id="ytick_4">
      <g id="line2d_10">
       <g>
-       <use style="stroke:#000000;stroke-width:0.8;" x="57.6" xlink:href="#m480ecff4e3" y="151.488"/>
+       <use style="stroke:#000000;stroke-width:0.8;" x="57.6" xlink:href="#mcf4dca2140" y="151.488"/>
       </g>
      </g>
      <g id="text_11">
@@ -346,7 +346,7 @@ L -3.5 0
     <g id="ytick_5">
      <g id="line2d_11">
       <g>
-       <use style="stroke:#000000;stroke-width:0.8;" x="57.6" xlink:href="#m480ecff4e3" y="103.488"/>
+       <use style="stroke:#000000;stroke-width:0.8;" x="57.6" xlink:href="#mcf4dca2140" y="103.488"/>
       </g>
      </g>
      <g id="text_12">
@@ -361,7 +361,7 @@ L -3.5 0
     <g id="ytick_6">
      <g id="line2d_12">
       <g>
-       <use style="stroke:#000000;stroke-width:0.8;" x="57.6" xlink:href="#m480ecff4e3" y="55.488"/>
+       <use style="stroke:#000000;stroke-width:0.8;" x="57.6" xlink:href="#mcf4dca2140" y="55.488"/>
       </g>
      </g>
      <g id="text_13">
@@ -577,7 +577,7 @@ z
     </g>
    </g>
    <g id="line2d_13">
-    <path clip-path="url(#p431c152dea)" d="M 73.832727 282.048 
+    <path clip-path="url(#p16eef5b12e)" d="M 73.832727 282.048 
 L 87.36 277.248 
 L 100.887273 270.528 
 L 114.414545 269.568 
@@ -597,7 +597,7 @@ L 290.269091 266.688
 L 303.796364 263.808 
 L 317.323636 278.208 
 L 330.850909 270.528 
-L 344.378182 289.728 
+L 344.378182 283.008 
 L 357.905455 289.728 
 L 371.432727 289.728 
 L 384.96 289.728 
@@ -605,7 +605,7 @@ L 398.487273 289.728
 " style="fill:none;stroke:#1f77b4;stroke-linecap:square;stroke-width:1.5;"/>
    </g>
    <g id="line2d_14">
-    <path clip-path="url(#p431c152dea)" d="M 73.832727 295.488 
+    <path clip-path="url(#p16eef5b12e)" d="M 73.832727 295.488 
 L 87.36 293.568 
 L 100.887273 295.488 
 L 114.414545 295.488 
@@ -633,7 +633,7 @@ L 398.487273 295.488
 " style="fill:none;stroke:#ff7f0e;stroke-linecap:square;stroke-width:1.5;"/>
    </g>
    <g id="line2d_15">
-    <path clip-path="url(#p431c152dea)" d="M 73.832727 232.128 
+    <path clip-path="url(#p16eef5b12e)" d="M 73.832727 232.128 
 L 87.36 218.688 
 L 100.887273 208.128 
 L 114.414545 191.808 
@@ -653,7 +653,7 @@ L 290.269091 176.448
 L 303.796364 143.808 
 L 317.323636 225.408 
 L 330.850909 140.928 
-L 344.378182 277.248 
+L 344.378182 237.888 
 L 357.905455 277.248 
 L 371.432727 277.248 
 L 384.96 277.248 
@@ -870,7 +870,7 @@ L 348.72625 83.926688
   </g>
  </g>
  <defs>
-  <clipPath id="p431c152dea">
+  <clipPath id="p16eef5b12e">
    <rect height="266.112" width="357.12" x="57.6" y="41.472"/>
   </clipPath>
  </defs>

2018/other/elf2c.py

@@ -19,7 +19,7 @@ def preamble():
                 int c = 0;
                 int d = 0;
                 int e = 0;
-                int f = 0;''')
+                int f = 0;\n''')
 
 
 def footer():

2018/src/day21.rs

@@ -1,9 +1,48 @@
+use std::collections::HashSet;
 use std::io::Read;
 
 use common::Solution;
 
 #[derive(Default)]
-pub struct Day21 {}
+pub struct Day21 {
+}
+
+struct ValidInputs {
+    f: i64
+}
+
+impl ValidInputs {
+    pub fn new(start: i64) -> Self {
+        ValidInputs {
+            f: start
+        }
+    }
+}
+
+impl Iterator for ValidInputs {
+    type Item = i64;
+
+    fn next(&mut self) -> Option<i64> {
+        let mut f = self.f;
+        let mut e = f | 0x10000;
+        f = 13284195;
+
+        loop {
+            let d = e & 0xff;
+            f += d;
+            f &= 0xffffff;
+            f *= 65899;
+            f &= 0xffffff;
+
+            if 0x100 > e {
+                self.f = f;
+                return Some(f);
+            }
+
+            e >>= 8;
+        }
+    }
+}
 
 impl Day21 {
     pub fn new() -> Self {
@@ -13,13 +52,22 @@ impl Day21 {
 
 impl Solution for Day21 {
     fn part1(&mut self, _input: &mut Read) -> String {
-        unimplemented!()
+        format!("{}", ValidInputs::new(0).next().unwrap())
     }
 
     fn part2(&mut self, _input: &mut Read) -> String {
-        unimplemented!()
+        let inputs = ValidInputs::new(0);
+        let mut seen = HashSet::new();
+        let mut last = None;
+
+        for input in inputs {
+            if seen.contains(&input) {
+                return format!("{}", last.unwrap());
+            } else {
+                last = Some(input);
+                seen.insert(input);
+            }
+        }
+        unreachable!();
     }
 }
-
-#[cfg(test)]
-mod tests {}