From fa5b9c2275b8e7e1d91575657b9ceb50eb014ef1 Mon Sep 17 00:00:00 2001
From: Ishan Jain <contact@ishanjain.me>
Date: Mon, 2 Jan 2023 15:58:24 +0530
Subject: [PATCH] optimized day 4

---
 src/day4/1.rs | 85 ++++++++++++++++++++++++---------------------------
 src/day4/2.rs | 85 ++++++++++++++++++++++++---------------------------
 2 files changed, 80 insertions(+), 90 deletions(-)

diff --git a/src/day4/1.rs b/src/day4/1.rs
index 51bac23..ef74083 100644
--- a/src/day4/1.rs
+++ b/src/day4/1.rs
@@ -10,9 +10,9 @@ fn solution(ip: &'static str) -> usize {
     let mut input: Vec<u8> = ip.bytes().collect();
     let l = input.len();
 
-    loop {
-        let mut t = vec![];
+    let mut t = Vec::with_capacity(32);
 
+    loop {
         let mut n = num;
         while n != 0 {
             let d = n % 10;
@@ -21,47 +21,48 @@ fn solution(ip: &'static str) -> usize {
             n /= 10;
         }
 
-        input.extend(t.into_iter().rev());
+        input.extend(t.iter().rev());
 
-        let c = md5_compute(input.clone());
+        let ans = md5_compute(&mut input);
 
-        if c[0..2] == [0, 0] && c[2] & 0b11110000 == 0 {
+        if ans.to_be() < 4096 {
             return num;
         }
 
         input.resize(l, 0);
 
+        t.clear();
+
         num += 1;
     }
 }
+// s specifies the per-round shift amounts
+const S: [u32; 64] = [
+    7, 12, 17, 22, 7, 12, 17, 22, 7, 12, 17, 22, 7, 12, 17, 22, // 0..15
+    5, 9, 14, 20, 5, 9, 14, 20, 5, 9, 14, 20, 5, 9, 14, 20, // 16..31
+    4, 11, 16, 23, 4, 11, 16, 23, 4, 11, 16, 23, 4, 11, 16, 23, // 32..47
+    6, 10, 15, 21, 6, 10, 15, 21, 6, 10, 15, 21, 6, 10, 15, 21, // 48..63
+];
+const K: [u32; 64] = [
+    0xd76aa478, 0xe8c7b756, 0x242070db, 0xc1bdceee, // 0..3
+    0xf57c0faf, 0x4787c62a, 0xa8304613, 0xfd469501, // 4..7
+    0x698098d8, 0x8b44f7af, 0xffff5bb1, 0x895cd7be, // 8..11
+    0x6b901122, 0xfd987193, 0xa679438e, 0x49b40821, // 12..15
+    0xf61e2562, 0xc040b340, 0x265e5a51, 0xe9b6c7aa, // 16..19
+    0xd62f105d, 0x02441453, 0xd8a1e681, 0xe7d3fbc8, //20..23
+    0x21e1cde6, 0xc33707d6, 0xf4d50d87, 0x455a14ed, // 24..27
+    0xa9e3e905, 0xfcefa3f8, 0x676f02d9, 0x8d2a4c8a, // 28..31
+    0xfffa3942, 0x8771f681, 0x6d9d6122, 0xfde5380c, // 32..35
+    0xa4beea44, 0x4bdecfa9, 0xf6bb4b60, 0xbebfbc70, // 36..39
+    0x289b7ec6, 0xeaa127fa, 0xd4ef3085, 0x04881d05, // 40..43
+    0xd9d4d039, 0xe6db99e5, 0x1fa27cf8, 0xc4ac5665, // 44..47
+    0xf4292244, 0x432aff97, 0xab9423a7, 0xfc93a039, // 48..51
+    0x655b59c3, 0x8f0ccc92, 0xffeff47d, 0x85845dd1, // 52..55
+    0x6fa87e4f, 0xfe2ce6e0, 0xa3014314, 0x4e0811a1, // 56..59
+    0xf7537e82, 0xbd3af235, 0x2ad7d2bb, 0xeb86d391, // 60..63
+];
 
-fn md5_compute(mut ip: Vec<u8>) -> [u8; 16] {
-    // s specifies the per-round shift amounts
-    const S: [u32; 64] = [
-        7, 12, 17, 22, 7, 12, 17, 22, 7, 12, 17, 22, 7, 12, 17, 22, // 0..15
-        5, 9, 14, 20, 5, 9, 14, 20, 5, 9, 14, 20, 5, 9, 14, 20, // 16..31
-        4, 11, 16, 23, 4, 11, 16, 23, 4, 11, 16, 23, 4, 11, 16, 23, // 32..47
-        6, 10, 15, 21, 6, 10, 15, 21, 6, 10, 15, 21, 6, 10, 15, 21, // 48..63
-    ];
-    const K: [u32; 64] = [
-        0xd76aa478, 0xe8c7b756, 0x242070db, 0xc1bdceee, // 0..3
-        0xf57c0faf, 0x4787c62a, 0xa8304613, 0xfd469501, // 4..7
-        0x698098d8, 0x8b44f7af, 0xffff5bb1, 0x895cd7be, // 8..11
-        0x6b901122, 0xfd987193, 0xa679438e, 0x49b40821, // 12..15
-        0xf61e2562, 0xc040b340, 0x265e5a51, 0xe9b6c7aa, // 16..19
-        0xd62f105d, 0x02441453, 0xd8a1e681, 0xe7d3fbc8, //20..23
-        0x21e1cde6, 0xc33707d6, 0xf4d50d87, 0x455a14ed, // 24..27
-        0xa9e3e905, 0xfcefa3f8, 0x676f02d9, 0x8d2a4c8a, // 28..31
-        0xfffa3942, 0x8771f681, 0x6d9d6122, 0xfde5380c, // 32..35
-        0xa4beea44, 0x4bdecfa9, 0xf6bb4b60, 0xbebfbc70, // 36..39
-        0x289b7ec6, 0xeaa127fa, 0xd4ef3085, 0x04881d05, // 40..43
-        0xd9d4d039, 0xe6db99e5, 0x1fa27cf8, 0xc4ac5665, // 44..47
-        0xf4292244, 0x432aff97, 0xab9423a7, 0xfc93a039, // 48..51
-        0x655b59c3, 0x8f0ccc92, 0xffeff47d, 0x85845dd1, // 52..55
-        0x6fa87e4f, 0xfe2ce6e0, 0xa3014314, 0x4e0811a1, // 56..59
-        0xf7537e82, 0xbd3af235, 0x2ad7d2bb, 0xeb86d391, // 60..63
-    ];
-
+fn md5_compute(ip: &mut Vec<u8>) -> u32 {
     let l = ip.len();
 
     // Padding
@@ -76,14 +77,14 @@ fn md5_compute(mut ip: Vec<u8>) -> [u8; 16] {
 
     ip.extend((l * 8).to_le_bytes());
 
-    let input: Vec<u32> = ip
-        .chunks(4)
-        .map(|chunk| u32::from_le_bytes([chunk[0], chunk[1], chunk[2], chunk[3]]))
-        .collect();
-
     let mut state: [u32; 4] = [0x67452301, 0xefcdab89, 0x98badcfe, 0x10325476];
 
-    for chunk in input.chunks(16) {
+    for chunk in ip.chunks(64).map(|chunk| {
+        chunk
+            .chunks(4)
+            .map(|c| u32::from_le_bytes([c[0], c[1], c[2], c[3]]))
+            .collect::<Vec<u32>>()
+    }) {
         let mut lstate = state;
 
         for i in 0..64 {
@@ -122,13 +123,7 @@ fn md5_compute(mut ip: Vec<u8>) -> [u8; 16] {
         state[3] += lstate[3];
     }
 
-    let mut hash = [0; 16];
-
-    for (i, c) in state.map(|c| c.to_le_bytes()).flatten().iter().enumerate() {
-        hash[i] = *c;
-    }
-
-    hash
+    state[0]
 }
 
 fn main() {
diff --git a/src/day4/2.rs b/src/day4/2.rs
index 1bf7557..2351ee7 100644
--- a/src/day4/2.rs
+++ b/src/day4/2.rs
@@ -10,9 +10,9 @@ fn solution(ip: &'static str) -> usize {
     let mut input: Vec<u8> = ip.bytes().collect();
     let l = input.len();
 
-    loop {
-        let mut t = vec![];
+    let mut t = Vec::with_capacity(32);
 
+    loop {
         let mut n = num;
         while n != 0 {
             let d = n % 10;
@@ -21,47 +21,48 @@ fn solution(ip: &'static str) -> usize {
             n /= 10;
         }
 
-        input.extend(t.into_iter().rev());
+        input.extend(t.iter().rev());
 
-        let c = md5_compute(input.clone());
+        let ans = md5_compute(&mut input);
 
-        if c[0..3] == [0, 0, 0] {
+        if ans.to_be() < 256 {
             return num;
         }
 
         input.resize(l, 0);
 
+        t.clear();
+
         num += 1;
     }
 }
+// s specifies the per-round shift amounts
+const S: [u32; 64] = [
+    7, 12, 17, 22, 7, 12, 17, 22, 7, 12, 17, 22, 7, 12, 17, 22, // 0..15
+    5, 9, 14, 20, 5, 9, 14, 20, 5, 9, 14, 20, 5, 9, 14, 20, // 16..31
+    4, 11, 16, 23, 4, 11, 16, 23, 4, 11, 16, 23, 4, 11, 16, 23, // 32..47
+    6, 10, 15, 21, 6, 10, 15, 21, 6, 10, 15, 21, 6, 10, 15, 21, // 48..63
+];
+const K: [u32; 64] = [
+    0xd76aa478, 0xe8c7b756, 0x242070db, 0xc1bdceee, // 0..3
+    0xf57c0faf, 0x4787c62a, 0xa8304613, 0xfd469501, // 4..7
+    0x698098d8, 0x8b44f7af, 0xffff5bb1, 0x895cd7be, // 8..11
+    0x6b901122, 0xfd987193, 0xa679438e, 0x49b40821, // 12..15
+    0xf61e2562, 0xc040b340, 0x265e5a51, 0xe9b6c7aa, // 16..19
+    0xd62f105d, 0x02441453, 0xd8a1e681, 0xe7d3fbc8, //20..23
+    0x21e1cde6, 0xc33707d6, 0xf4d50d87, 0x455a14ed, // 24..27
+    0xa9e3e905, 0xfcefa3f8, 0x676f02d9, 0x8d2a4c8a, // 28..31
+    0xfffa3942, 0x8771f681, 0x6d9d6122, 0xfde5380c, // 32..35
+    0xa4beea44, 0x4bdecfa9, 0xf6bb4b60, 0xbebfbc70, // 36..39
+    0x289b7ec6, 0xeaa127fa, 0xd4ef3085, 0x04881d05, // 40..43
+    0xd9d4d039, 0xe6db99e5, 0x1fa27cf8, 0xc4ac5665, // 44..47
+    0xf4292244, 0x432aff97, 0xab9423a7, 0xfc93a039, // 48..51
+    0x655b59c3, 0x8f0ccc92, 0xffeff47d, 0x85845dd1, // 52..55
+    0x6fa87e4f, 0xfe2ce6e0, 0xa3014314, 0x4e0811a1, // 56..59
+    0xf7537e82, 0xbd3af235, 0x2ad7d2bb, 0xeb86d391, // 60..63
+];
 
-fn md5_compute(mut ip: Vec<u8>) -> [u8; 16] {
-    // s specifies the per-round shift amounts
-    const S: [u32; 64] = [
-        7, 12, 17, 22, 7, 12, 17, 22, 7, 12, 17, 22, 7, 12, 17, 22, // 0..15
-        5, 9, 14, 20, 5, 9, 14, 20, 5, 9, 14, 20, 5, 9, 14, 20, // 16..31
-        4, 11, 16, 23, 4, 11, 16, 23, 4, 11, 16, 23, 4, 11, 16, 23, // 32..47
-        6, 10, 15, 21, 6, 10, 15, 21, 6, 10, 15, 21, 6, 10, 15, 21, // 48..63
-    ];
-    const K: [u32; 64] = [
-        0xd76aa478, 0xe8c7b756, 0x242070db, 0xc1bdceee, // 0..3
-        0xf57c0faf, 0x4787c62a, 0xa8304613, 0xfd469501, // 4..7
-        0x698098d8, 0x8b44f7af, 0xffff5bb1, 0x895cd7be, // 8..11
-        0x6b901122, 0xfd987193, 0xa679438e, 0x49b40821, // 12..15
-        0xf61e2562, 0xc040b340, 0x265e5a51, 0xe9b6c7aa, // 16..19
-        0xd62f105d, 0x02441453, 0xd8a1e681, 0xe7d3fbc8, //20..23
-        0x21e1cde6, 0xc33707d6, 0xf4d50d87, 0x455a14ed, // 24..27
-        0xa9e3e905, 0xfcefa3f8, 0x676f02d9, 0x8d2a4c8a, // 28..31
-        0xfffa3942, 0x8771f681, 0x6d9d6122, 0xfde5380c, // 32..35
-        0xa4beea44, 0x4bdecfa9, 0xf6bb4b60, 0xbebfbc70, // 36..39
-        0x289b7ec6, 0xeaa127fa, 0xd4ef3085, 0x04881d05, // 40..43
-        0xd9d4d039, 0xe6db99e5, 0x1fa27cf8, 0xc4ac5665, // 44..47
-        0xf4292244, 0x432aff97, 0xab9423a7, 0xfc93a039, // 48..51
-        0x655b59c3, 0x8f0ccc92, 0xffeff47d, 0x85845dd1, // 52..55
-        0x6fa87e4f, 0xfe2ce6e0, 0xa3014314, 0x4e0811a1, // 56..59
-        0xf7537e82, 0xbd3af235, 0x2ad7d2bb, 0xeb86d391, // 60..63
-    ];
-
+fn md5_compute(ip: &mut Vec<u8>) -> u32 {
     let l = ip.len();
 
     // Padding
@@ -76,14 +77,14 @@ fn md5_compute(mut ip: Vec<u8>) -> [u8; 16] {
 
     ip.extend((l * 8).to_le_bytes());
 
-    let input: Vec<u32> = ip
-        .chunks(4)
-        .map(|chunk| u32::from_le_bytes([chunk[0], chunk[1], chunk[2], chunk[3]]))
-        .collect();
-
     let mut state: [u32; 4] = [0x67452301, 0xefcdab89, 0x98badcfe, 0x10325476];
 
-    for chunk in input.chunks(16) {
+    for chunk in ip.chunks(64).map(|chunk| {
+        chunk
+            .chunks(4)
+            .map(|c| u32::from_le_bytes([c[0], c[1], c[2], c[3]]))
+            .collect::<Vec<u32>>()
+    }) {
         let mut lstate = state;
 
         for i in 0..64 {
@@ -122,13 +123,7 @@ fn md5_compute(mut ip: Vec<u8>) -> [u8; 16] {
         state[3] += lstate[3];
     }
 
-    let mut hash = [0; 16];
-
-    for (i, c) in state.map(|c| c.to_le_bytes()).flatten().iter().enumerate() {
-        hash[i] = *c;
-    }
-
-    hash
+    state[0]
 }
 
 fn main() {