1 files changed, 52 insertions, 0 deletions
diff --git a/2017/src/bin/day_12.rs b/2017/src/bin/day_12.rs
new file mode 100644
index 0000000..39f05e9
--- /dev/null
+++ b/2017/src/bin/day_12.rs
@@ -0,0 +1,52 @@
+extern crate advent_of_code_2017;
+use advent_of_code_2017::*;
+
+use std::cmp;
+
+fn main() {
+    let args = AdventArgs::init();
+
+    let mut groups: Vec<Vec<i32>> = vec!(vec!(0)); //0 in the first group
+
+    for line in args.input {
+        let mut words_iter = line.split_whitespace();
+        let current: i32 = words_iter.next().unwrap().parse().unwrap();
+        if find_group(&groups, current).is_none() {
+            groups.push(vec!(current));
+        }
+        words_iter.next().unwrap(); //<->
+        for other_str in words_iter {
+            let other: i32 = other_str.trim_right_matches(",").parse().unwrap();
+
+            match (find_group(&groups, current), find_group(&groups, other)) {
+                (Some(current_group), Some(other_group)) if current_group != other_group => {
+                    merge_groups(&mut groups, current_group, other_group);
+                },
+                (Some(_), Some(_)) => {
+                },
+                (Some(current_group), None) => {
+                    groups[current_group].push(other);
+                },
+                (None, _) => panic!("Current group not found!")
+            };
+        }
+    }
+
+    if args.part == 1 {
+        println!("First group has {} members", groups[0].len());
+    } else {
+        println!("Total of {} groups", groups.len());
+    }
+}
+
+fn find_group(groups: &Vec<Vec<i32>>, x: i32) -> Option<usize> {
+    groups.iter().position(|group| group.contains(&x))
+}
+
+fn merge_groups(groups: &mut Vec<Vec<i32>>, a: usize, b: usize) {
+    let src = cmp::max(a, b);
+    let dest = cmp::min(a, b);
+
+    let mut from = groups.swap_remove(src);
+    groups[dest].append(&mut from)
+}