day14pt2

1 files changed, 117 insertions, 12 deletions

diff --git a/src/day14pt2.rs b/src/day14pt2.rs
index 9b68f62..a5d5bed 100644
--- a/src/day14pt2.rs
+++ b/src/day14pt2.rs
@@ -1,23 +1,128 @@
+fn cycle(input: &mut Vec<Vec<char>>) {
+    let mut sl: usize;
+
+    // north
+    for j in 0..input[0].len() {
+        sl = 0;
+        for i in 0..input.len() {
+            if input[i][j] == 'O' {
+                if sl != i {
+                    input[sl][j] = 'O';
+                    input[i][j] = '.';
+                }
+                sl += 1;
+            } else if input[i][j] == '#' {
+                sl = i + 1;
+            }
+        }
+    }
+
+    // west
+    for i in 0..input.len() {
+        sl = 0;
+        for j in 0..input[0].len() {
+            if input[i][j] == 'O' {
+                if sl != j {
+                    input[i][sl] = 'O';
+                    input[i][j] = '.';
+                }
+                sl += 1;
+            } else if input[i][j] == '#' {
+                sl = j + 1;
+            }
+        }
+    }
+
+    // south
+    for j in 0..input[0].len() {
+        sl = input.len() - 1;
+        for i in (0..input.len()).rev() {
+            if input[i][j] == 'O' {
+                if sl != i {
+                    input[sl][j] = 'O';
+                    input[i][j] = '.';
+                }
+                if i != 0 {
+                    sl -= 1;
+                }
+            } else if input[i][j] == '#' {
+                if i != 0 {
+                    sl = i - 1;
+                }
+            }
+        }
+    }
+
+    // east
+    for i in 0..input.len() {
+        sl = input[0].len() - 1;
+        for j in (0..input[0].len()).rev() {
+            if input[i][j] == 'O' {
+                if sl != j {
+                    input[i][sl] = 'O';
+                    input[i][j] = '.';
+                }
+                if j != 0 {
+                    sl -= 1;
+                }
+            } else if input[i][j] == '#' {
+                if j != 0 {
+                    sl = j - 1;
+                }
+            }
+        }
+    }
+}
+
+fn sum(input: &Vec<Vec<char>>) -> u64 {
+    let mut sum: u64 = 0;
+
+    for i in 0..input.len() {
+        for j in 0..input[0].len() {
+            if input[i][j] == 'O' {
+                sum += (input.len() - i) as u64;
+            }
+        }
+    }
+
+    return sum;
+}
+
+fn cycle_len(a: &Vec<u64>) -> u64 {
+    for cl in 2..(a.len() / 3) {
+        let mut ind = true;
+        for i in 0..cl {
+            if a[i] != a[cl + i] || a[cl + i] != a[cl * 2 + i] {
+                ind = false;
+                break;
+            }
+        }
+        if ind {
+            return cl as u64;
+        }
+    }
+    return 0;
+}
+
 pub fn main() {
     let txt = std::fs::read_to_string("./input/day14.txt").unwrap();
-    let input = txt
+    let mut input = txt
         .lines()
         .map(|s| s.chars().collect::<Vec<char>>())
         .collect::<Vec<Vec<char>>>();
 
-    let mut sum: u64 = 0;
 
-    for j in 0..input[0].len() {
-        let mut off: u64 = 0;
-        for i in 0..input.len() {
-            if input[i][j] == 'O' {
-                sum += input.len() as u64 - off;
-                off += 1;
-            } else if input[i][j] == '#' {
-                off = (i + 1) as u64;
-            }
+    let mut a = vec![];
+    for i in 0..1000 {
+        cycle(&mut input);
+        if i > 500 {
+            a.push(sum(&input));
         }
     }
 
-    println!("{}", sum);
+    let cl = cycle_len(&a);
+    assert_ne!(cl, 0);
+
+    let c = 1000000000 - 501 - 1;
+    println!("{}", a[(c % cl) as usize]);
 }