implement minor optimizations for day 2

README.md

@@ -12,12 +12,12 @@ Solutions for [Advent of Code](https://adventofcode.com/) in [Rust](https://www.
 | Day | Part 1 | Part 2 |
 | :---: | :---: | :---:  |
 | [Day 1](./src/bin/01.rs) | `881.1µs` | `849.0µs` |
-| [Day 2](./src/bin/02.rs) | `225.7ms` | `250.4ms` |
+| [Day 2](./src/bin/02.rs) | `81.3ms` | `84.4ms` |
 | [Day 3](./src/bin/03.rs) | `85.9µs` | `120.1µs` |
 | [Day 4](./src/bin/04.rs) | `227.4µs` | `1.9ms` |
 | [Day 5](./src/bin/05.rs) | `159.6µs` | `21.4µs` |
 
-**Total: 480.34ms**
+**Total: 169.94ms**
 <!--- benchmarking table --->
 
 ---

src/bin/02.rs

@@ -5,15 +5,12 @@ pub fn part_one(input: &str) -> Option<u64> {
     let mut sum: u64 = 0;
     for range in input.split(',') {
         // println!("Range is: {}", range);
-        let values = range.split('-').map(|v| v.trim().parse::<u64>().unwrap()).collect::<Vec<u64>>();
+        let values = range.split('-').map(|v| v.trim().parse::<u64>().unwrap()).collect_vec();
         let start = values[0];
         let end = values[1];
         // println!("Range: {}-{}", start, end);
-        for n in start..=end {
+        for n in (start..=end).filter(|n| n.to_string().len() % 2 == 0) {
             let s = n.to_string();
-            if s.chars().collect_vec().len() % 2 != 0 {
-                continue;
-            }
             let first_half = &s[0..(s.len() / 2)];
             let second_half = &s[(s.len() / 2)..s.len()];
             if first_half == second_half {
@@ -29,17 +26,14 @@ pub fn part_two(input: &str) -> Option<u64> {
     let mut sum: u64 = 0;
     for range in input.split(',') {
         // println!("Range is: {}", range);
-        let values = range.split('-').map(|v| v.trim().parse::<u64>().unwrap()).collect::<Vec<u64>>();
+        let values = range.split('-').map(|v| v.trim().parse::<u64>().unwrap()).collect_vec();
         let start = values[0];
         let end = values[1];
         // println!("Range: {}-{}", start, end);
         for n in start..=end {
             let s = n.to_string();
-            let total_chars = s.chars().collect_vec().len();
+            let total_chars = (n as f64).log10().floor() as usize + 1;
-            'takeBy: for take_by in 1..=(total_chars / 2) {
+            'takeBy: for take_by in (1..=(total_chars / 2)).filter(|tb| total_chars % tb == 0) {
-                if total_chars % take_by != 0 {
-                    continue;
-                }
                 let mut idx = 0;
                 while idx + 2 * take_by <= total_chars {
                     let part = &s[idx..(idx + take_by)];