Add day 20

day20_test.txt

@@ -0,0 +1,7 @@
+1
+2
+-3
+3
+-2
+0
+4

src/day20/main.rs

@@ -1,3 +1,52 @@
-fn main() {
-    println!("Not ready");
+use base::read_file;
+
+fn do_encryption(key: &Vec<(usize, i64)>, data: &mut Vec<(usize, i64)>) {
+    let wrap_size = data.len() - 1;
+    for (index_to_find, enc_datum) in key {
+        let index = data.iter().position(|(org_index, _)| org_index == index_to_find).unwrap();
+        if *enc_datum == 0 {
+            continue;
+        }
+
+        let element = data.remove(index);
+
+        if *enc_datum > 0 {
+            let enc_datum = *enc_datum as usize;
+            data.rotate_left((enc_datum % wrap_size) as usize);
+        } else {
+            let enc_datum = enc_datum.abs() as usize;
+            data.rotate_right((enc_datum % wrap_size) as usize);
+        }
+
+        data.insert(index, element);
+    }
+}
+
+fn calc_result(data: Vec<(usize, i64)>) -> i64 {
+    let zero_index = data.iter().position(|(_, value)| *value == 0).unwrap();
+    println!("Found zero at {}", zero_index);
+    let wrap_size = data.len();
+    let number_1 = data[(zero_index + 1000) % wrap_size].1;
+    let number_2 = data[(zero_index + 2000) % wrap_size].1;
+    let number_3 = data[(zero_index + 3000) % wrap_size].1;
+
+    number_1 + number_2 + number_3
+}
+
+fn main() {
+    let enc_data = read_file("day20.txt").iter().filter_map(|line| line.parse().ok()).enumerate().collect::<Vec<(usize, i64)>>();
+
+    let mut result = enc_data.clone();
+    do_encryption(&enc_data, &mut result);
+
+
+    println!("Task 1: {}", calc_result(result));
+
+    let enc_data = enc_data.iter().map(|(idx, value)| (*idx, value * 811589153)).collect::<Vec<_>>();
+    let mut result = enc_data.clone();
+    for _ in 0..10 {
+        do_encryption(&enc_data, &mut result);
+    }
+
+    println!("Task 2: {}", calc_result(result));
 }