From c20eb0ca69e6c62efe60271372513ed39f463da6 Mon Sep 17 00:00:00 2001
From: Samuel Ortion <samuel+git@ortion.fr>
Date: Fri, 1 Dec 2023 13:40:17 +0100
Subject: [PATCH] day1 part2 solved

---
 days/.gitignore           |  2 ++
 days/01/part2/src/main.rs | 31 +++++++++++++++++++++++++++----
 2 files changed, 29 insertions(+), 4 deletions(-)

diff --git a/days/.gitignore b/days/.gitignore
index 6985cf1..afea973 100755
--- a/days/.gitignore
+++ b/days/.gitignore
@@ -1,3 +1,5 @@
+data
+
 # Generated by Cargo
 # will have compiled files and executables
 debug/
diff --git a/days/01/part2/src/main.rs b/days/01/part2/src/main.rs
index 1f654a7..bfb3aee 100644
--- a/days/01/part2/src/main.rs
+++ b/days/01/part2/src/main.rs
@@ -1,3 +1,5 @@
+use std::cmp;
+use std::collections::HashMap;
 use std::fs;
 
 // Extract all numbers, digits and letter written digits
@@ -5,6 +7,26 @@ fn extract_numbers(line: &str) -> Vec<u32> {
     let written_digits: Vec<&str> = vec![
         "one", "two", "three", "four", "five", "six", "seven", "eight", "nine",
     ];
+    let mut max_tail_overlaps: HashMap<&str, u32> = HashMap::new();
+    // Compute the size of the suffix of number i overlaping with prefix of number j:
+    for suffix_number in &written_digits {
+        max_tail_overlaps.insert(suffix_number.clone(), 0);
+        for prefix_number in &written_digits {
+            if suffix_number != prefix_number {
+                let mut overlap: u32 = 0;
+                for i in 0..(cmp::min(prefix_number.len(), suffix_number.len())) {
+                    if suffix_number.chars().nth_back(i) == prefix_number.chars().nth(i) {
+                        overlap += 1;
+                    } else {
+                        break;
+                    }
+                }
+                if overlap > max_tail_overlaps[suffix_number] {
+                    max_tail_overlaps.insert(suffix_number, overlap);
+                }
+            }
+        }
+    }
     let mut numbers: Vec<u32> = Vec::new();
     let mut current_digit_word: String = "".to_owned();
     for character in line.chars() {
@@ -19,12 +41,13 @@ fn extract_numbers(line: &str) -> Vec<u32> {
                 let positions: Vec<(usize, &str)> =
                     current_digit_word.match_indices(digit_writing).collect();
                 if positions.len() > 0 {
-                    let start_position = positions[0].0;
-                    let end_position = start_position + word_length;
-                    let current_digit_word_slice = &current_digit_word[end_position..];
-                    current_digit_word = current_digit_word_slice.to_owned();
                     let digit = index as u32 + 1;
                     numbers.push(digit);
+                    let start_position = positions[0].0;
+                    let end_position =
+                        start_position + word_length - max_tail_overlaps[digit_writing] as usize;
+                    let current_digit_word_slice = &current_digit_word[end_position..];
+                    current_digit_word = current_digit_word_slice.to_owned();
                 }
             }
         }