1 files changed, 153 insertions, 0 deletions
diff --git a/d07/src/main.rs b/d07/src/main.rs
new file mode 100644
index 0000000..ef53b6e
--- /dev/null
+++ b/d07/src/main.rs
@@ -0,0 +1,153 @@
+use std::fs;
+
+fn solve_part1(lines: &Vec<&str>) -> usize {
+    let mut total_tls = 0;
+
+    for line in lines {
+        let chars: Vec<char> = line.chars().collect();
+
+        let mut has_tls = false;
+        let mut in_brackets = false;
+        for i in 0..chars.len() - 3 {
+            // Are we entering/leaving a "hypernet sequence"?
+            if chars[i] == '[' {
+                in_brackets = true;
+            } else if chars[i] == ']' {
+                in_brackets = false;
+            }
+
+            // Check for ABBA pattern to know if address has TLS
+            let ch0 = chars[i];
+            let ch1 = chars[i + 1];
+            if ch0 != ch1 && chars[i + 3] == ch0 && chars[i + 2] == ch1 {
+                if !in_brackets {
+                    has_tls = true;
+                } else {
+                    // Reject if an ABBA occurs in brackets
+                    has_tls = false;
+                    break;
+                }
+            }
+        }
+
+        if has_tls {
+            total_tls += 1;
+        }
+    }
+
+    total_tls
+}
+
+fn solve_part2(lines: &Vec<&str>) -> usize {
+    let mut total_ssl = 0;
+
+    for line in lines {
+        let chars: Vec<char> = line.chars().collect();
+
+        let mut has_ssl = false;
+        let mut in_brack_aba = false;
+        'outer: for i in 0..chars.len() - 2 {
+            // Are we entering/leaving brackets on our ABA search?
+            if chars[i] == '[' {
+                in_brack_aba = true;
+            } else if chars[i] == ']' {
+                in_brack_aba = false;
+            }
+
+            // Check for ABA pattern
+            let ch0 = chars[i];
+            let ch1 = chars[i + 1];
+            if !in_brack_aba && ch0 != ch1 && chars[i + 2] == ch0 {
+                // If ABA was found, check entire address for BAB
+                let mut in_brack_bab = false;
+                for j in 0..chars.len() - 2 {
+                    // Are we entering/leaving brackets on our BAB search?
+                    if chars[j] == '[' {
+                        in_brack_bab = true;
+                    } else if chars[j] == ']' {
+                        in_brack_bab = false;
+                    }
+
+                    if chars[j] == ch1 && chars[j + 1] == ch0 && chars[j + 2] == ch1 {
+                        // BAB must be in square brackets
+                        if in_brack_bab {
+                            has_ssl = true;
+                            break 'outer;
+                        }
+                    }
+                }
+            }
+        }
+
+        if has_ssl {
+            total_ssl += 1;
+        }
+    }
+
+    total_ssl
+}
+
+fn main() {
+    // Read address list from input text file
+    let input = fs::read_to_string("input.txt").unwrap();
+    let lines = input.lines().collect();
+
+    // Part 1 gives 118 for me
+    println!("Part 1 solution: {}", solve_part1(&lines));
+
+    // Part 2 gives 260 for me
+    println!("Part 2 solution: {}", solve_part2(&lines));
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn part1_example1() {
+        let lines = vec!["abba[mnop]qrst"];
+        assert_eq!(solve_part1(&lines), 1);
+    }
+
+    #[test]
+    fn part1_example2() {
+        let lines = vec!["abcd[bddb]xyyx"];
+        assert_eq!(solve_part1(&lines), 0);
+    }
+
+    #[test]
+    fn part1_example3() {
+        let lines = vec!["aaaa[qwer]tyui"];
+        assert_eq!(solve_part1(&lines), 0);
+    }
+
+    #[test]
+    fn part1_example4() {
+        let lines = vec!["ioxxoj[asdfgh]zxcvbn"];
+        assert_eq!(solve_part1(&lines), 1);
+    }
+
+    #[test]
+    fn part2_example1() {
+        let lines = vec!["aba[bab]xyz"];
+        assert_eq!(solve_part2(&lines), 1);
+    }
+
+    #[test]
+    fn part2_example2() {
+        let lines = vec!["xyx[xyx]xyx"];
+        assert_eq!(solve_part2(&lines), 0);
+    }
+
+    #[test]
+    fn part2_example3() {
+        let lines = vec!["aaa[kek]eke"];
+        assert_eq!(solve_part2(&lines), 1);
+    }
+
+    #[test]
+    fn part2_example4() {
+        let lines = vec!["zazbz[bzb]cdb"];
+        assert_eq!(solve_part2(&lines), 1);
+    }
+}