Day 6: memory rebalancing

3 files changed, 65 insertions, 0 deletions

diff --git a/inputs/day_6.txt b/inputs/day_6.txt
new file mode 100644
index 0000000..b16e11b
--- /dev/null
+++ b/inputs/day_6.txt
@@ -0,0 +1 @@
+4	10	4	1	8	4	9	14	5	1	14	15	0	15	3	5
diff --git a/src/bin/day_6.rs b/src/bin/day_6.rs
new file mode 100644
index 0000000..be9a515
--- /dev/null
+++ b/src/bin/day_6.rs
@@ -0,0 +1,61 @@
+extern crate advent_of_code_2017;
+use advent_of_code_2017::*;
+
+fn main() {
+    let args = AdventArgs::init();
+
+    let init_layout = parse_space_separated_ints(&args.input[0]).unwrap();
+    
+    let mut layouts = vec!(init_layout);
+    let mut balances = 0;
+    let mut cycle_found = false;
+    let mut cycle_size = 0;
+
+    while !cycle_found {
+        balances += 1;
+        let new_layout = find_next_layout(&layouts);
+        
+        if let Some(index) = layouts.iter().position(|x| *x == new_layout) {
+            cycle_found = true;
+            cycle_size = layouts.len() - index;
+        };
+        
+        layouts.push(new_layout);
+    }
+
+    if args.part == 1 {
+        println!("Did {} rebalances", balances);
+    } else {
+        println!("Cycle was {} long", cycle_size);
+    }
+}
+
+fn find_next_layout(layouts: &Vec<Vec<i32>>) -> Vec<i32> {
+    let previous_layout = layouts.last().unwrap();
+    rebalance(&previous_layout)
+}
+
+fn rebalance(layout: &Vec<i32>) -> Vec<i32> {
+    let biggest_container = layout.iter()
+        .enumerate()
+        .max_by(|&(ai, &asize), &(bi, &bsize)| {
+            asize.cmp(&bsize).then(bi.cmp(&ai))
+        })
+        .map(|(i, _)| i)
+        .unwrap();
+
+    
+    let mut new_layout = layout.clone();
+    let mut to_redistribute = new_layout[biggest_container];
+    new_layout[biggest_container] = 0;
+    let mut target = (biggest_container + 1) % layout.len();
+
+    while to_redistribute > 0 {
+        new_layout[target] += 1;
+        to_redistribute -= 1;
+        target = (target + 1) % layout.len();
+    }
+
+    new_layout
+}
+
diff --git a/src/lib.rs b/src/lib.rs
index caa8881..2a7b73a 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -62,6 +62,9 @@ impl AdventArgs {
     pub fn one_number_input(&self) -> Result<i32, std::num::ParseIntError> {
         self.input[0].parse()
     }
+    pub fn number_per_line_input(&self) -> Result<Vec<i32>, std::num::ParseIntError> {
+        self.input.iter().map(|line| line.parse()).collect()
+    }
 }
 
 pub fn parse_space_separated_ints(line: &String) -> Result<Vec<i32>, std::num::ParseIntError> {