From d252dc64c44942cc2ac3e5785458c64ef1437383 Mon Sep 17 00:00:00 2001
From: Greg Burri <greg.burri@gmail.com>
Date: Wed, 11 Dec 2024 20:10:57 +0100
Subject: [PATCH] Optimize a bit day 11: reduce to 1.9 ms

---
 src/day07.rs |  2 +-
 src/day11.rs | 16 ++++++----------
 src/utils.rs | 21 +++++++--------------
 3 files changed, 14 insertions(+), 25 deletions(-)

diff --git a/src/day07.rs b/src/day07.rs
index 0ed8919..05d23e1 100644
--- a/src/day07.rs
+++ b/src/day07.rs
@@ -70,7 +70,7 @@ pub fn sum_valid_equations_with_concat(equations: &[Equation]) -> i64 {
                 return true;
             }
 
-            let p = 10i64.pow(utils::nb_of_digits(last));
+            let p = 10i64.pow(utils::nb_of_digits_i64(last));
             if sub % p == 0 {
                 if is_valid(sub / p, &operands[0..l - 1]) {
                     return true;
diff --git a/src/day11.rs b/src/day11.rs
index 5567a16..c3e3bd1 100644
--- a/src/day11.rs
+++ b/src/day11.rs
@@ -18,24 +18,20 @@ fn add_or_set(map: &mut Stones, k: u64, n: u64) {
 
 pub fn blink(mut stones: Stones, i: u32) -> Stones {
     for _ in 0..i {
-        let mut next_stones = Stones::default();
-        for (stone, n) in stones {
+        for (stone, n) in stones.drain().collect::<Vec<_>>() {
             if stone == 0 {
-                add_or_set(&mut next_stones, 1, n);
+                add_or_set(&mut stones, 1, n);
             } else {
-                let nb_digits = utils::nb_of_digits(stone);
+                let nb_digits = utils::nb_of_digits_u64(stone);
                 if nb_digits % 2 == 0 {
                     let base = 10u64.pow(nb_digits / 2);
-                    let left = stone / base;
-                    let right = stone - left * base;
-                    add_or_set(&mut next_stones, left, n);
-                    add_or_set(&mut next_stones, right, n);
+                    add_or_set(&mut stones, stone / base, n);
+                    add_or_set(&mut stones, stone % base, n);
                 } else {
-                    add_or_set(&mut next_stones, stone * 2024, n);
+                    add_or_set(&mut stones, stone * 2024, n);
                 }
             }
         }
-        stones = next_stones;
     }
     stones
 }
diff --git a/src/utils.rs b/src/utils.rs
index a2a1d8d..d9ed680 100644
--- a/src/utils.rs
+++ b/src/utils.rs
@@ -1,6 +1,4 @@
-use std::{cmp, fmt::Debug, str::FromStr};
-
-use num;
+use std::{fmt::Debug, str::FromStr};
 
 pub fn split_to_vec<T>(str: &str, pat: &str) -> Vec<T>
 where
@@ -10,15 +8,10 @@ where
     str.split(pat).map(|v| v.parse::<T>().unwrap()).collect()
 }
 
-pub fn nb_of_digits<T>(mut v: T) -> u32
-where
-    T: cmp::PartialOrd<T> + std::ops::DivAssign<T> + num::FromPrimitive + Copy,
-{
-    let ten = T::from_u32(10).unwrap();
-    let mut n = 1;
-    while v >= ten {
-        v /= ten;
-        n += 1;
-    }
-    n
+pub fn nb_of_digits_u64(v: u64) -> u32 {
+    v.ilog10() + 1
+}
+
+pub fn nb_of_digits_i64(v: i64) -> u32 {
+    v.ilog10() + 1
 }
-- 
2.45.2