1 files changed, 63 insertions, 0 deletions
diff --git a/aoc7/src/main.rs b/aoc7/src/main.rs
new file mode 100644
index 0000000..e4689d2
--- /dev/null
+++ b/aoc7/src/main.rs
@@ -0,0 +1,63 @@
+use std::io::BufReader;
+use std::io::prelude::*;
+use std::fs::File;
+
+fn main() {
+    let lines = read_file();
+    let mut abba_count = 0;
+    for line in lines {
+        let mut in_squares = false;
+        let mut char_buffer = [' '; 4];
+
+        let mut chars = line.chars();
+        char_buffer[0] = chars.next().unwrap();
+        char_buffer[1] = chars.next().unwrap();
+        char_buffer[2] = chars.next().unwrap();
+        char_buffer[3] = chars.next().unwrap();
+        let mut abba_found = is_abba(char_buffer);
+        
+        for c in chars {
+            match c {
+                '[' => {in_squares = true;},
+                ']' => {in_squares = false;},
+                _ => {}
+            }
+            char_buffer[0] = char_buffer[1];
+            char_buffer[1] = char_buffer[2];
+            char_buffer[2] = char_buffer[3];
+            char_buffer[3] = c;
+
+            if is_abba(char_buffer) {
+                if in_squares {
+                    abba_found = false;
+                    break;
+                } else {
+                    abba_found = true;
+                }
+            }
+        }
+
+        if abba_found {
+            abba_count += 1;
+        }
+    }
+    println!("ABBA_count: {}", abba_count);
+}
+
+fn read_file() -> Vec<String> {
+    let file = BufReader::new(File::open("input.txt").unwrap());
+    file.lines()
+        .map(|line| line.unwrap().trim().to_string())
+        .filter(|line| line.len() > 0)
+        .collect()
+}
+
+fn is_abba(char_buffer: [char; 4]) -> bool {
+    char_buffer[0] != char_buffer[1] &&
+    char_buffer[0] == char_buffer[3] &&
+        char_buffer[1] == char_buffer[2] &&
+        char_buffer[0] != ']' &&
+        char_buffer[1] != ']' &&
+        char_buffer[0] != '[' &&
+        char_buffer[1] != '['
+}