finish day20

Author: coding-by-sea

examples/day_20.rs

@@ -0,0 +1,9 @@
+use aoc_2022::day_20::{parsing, part_1, part_2};
+use aoc_2022::utils;
+
+fn main() {
+    let lines = utils::read_lines("inputs/day_20").unwrap();
+    let nums = parsing(&lines);
+    println!("part 1: {}", part_1(&nums));
+    println!("part 2: {}", part_2(&nums));
+}

src/day_20.rs

@@ -0,0 +1,42 @@
+use std::str::FromStr;
+
+pub fn parsing(lines: &Vec<String>) -> Vec<i32> {
+    lines.iter().map(|x| i32::from_str(x).unwrap()).collect()
+}
+
+pub fn part_1(nums: &Vec<i32>) -> i32 {
+    let cycle = nums.len() as i32;
+    let mut nums_positions= (0..cycle as usize).collect::<Vec<usize>>();
+    let mut zero_original_pos = 0;
+    for (i, num) in nums.iter().enumerate() {
+        let pos = (nums_positions.iter().position(|x| *x == i).unwrap()) as i32;
+        let step = (*num).rem_euclid(cycle-1);
+        for i in 0..step {
+            (nums_positions[(pos+i).rem_euclid(cycle) as usize], nums_positions[(pos+i+1).rem_euclid(cycle) as usize]) = (nums_positions[(pos+i+1).rem_euclid(cycle) as usize], nums_positions[(pos+i).rem_euclid(cycle) as usize]);
+        }
+        if *num == 0 {
+            zero_original_pos = i;
+        }
+    }
+    let zero_pos = (nums_positions.iter().position(|x| *x == zero_original_pos).unwrap()) as i32;
+    nums[nums_positions[(zero_pos+1000).rem_euclid(cycle) as usize]] + nums[nums_positions[(zero_pos+2000).rem_euclid(cycle) as usize]] + nums[nums_positions[(zero_pos+3000).rem_euclid(cycle) as usize]]
+}
+
+pub fn part_2(nums: &Vec<i32>) -> i64 {
+    let cycle = nums.len() as i32;
+    let mut nums_positions= (0..cycle as usize).collect::<Vec<usize>>();
+    let mut zero_original_pos = 0;
+    for (i, num) in nums.iter().enumerate().cycle().take((cycle * 10) as usize) {
+        let pos = (nums_positions.iter().position(|x| *x == i).unwrap()) as i32;
+        let step = ((811589153 as i32).rem_euclid(cycle-1) * (*num).rem_euclid(cycle-1)).rem_euclid(cycle-1);
+        for i in 0..step {
+            (nums_positions[(pos+i).rem_euclid(cycle) as usize], nums_positions[(pos+i+1).rem_euclid(cycle) as usize]) = (nums_positions[(pos+i+1).rem_euclid(cycle) as usize], nums_positions[(pos+i).rem_euclid(cycle) as usize]);
+        }
+        if *num == 0 {
+            zero_original_pos = i;
+        }
+    }
+    // println!("{:?}", nums_positions);
+    let zero_pos = (nums_positions.iter().position(|x| *x == zero_original_pos).unwrap()) as i32;
+    (811589153 as i64) * (nums[nums_positions[(zero_pos+1000).rem_euclid(cycle) as usize]] + nums[nums_positions[(zero_pos+2000).rem_euclid(cycle) as usize]] + nums[nums_positions[(zero_pos+3000).rem_euclid(cycle) as usize]]) as i64
+}

src/lib.rs

@@ -19,3 +19,4 @@ pub mod day_15;
 pub mod day_16;
 pub mod day_17;
 pub mod day_18;
+pub mod day_20;