day3 completed

day3/Cargo.lock

@@ -5,3 +5,21 @@ version = 3
 [[package]]
 name = "day3"
 version = "0.1.0"
+dependencies = [
+ "itertools",
+]
+
+[[package]]
+name = "either"
+version = "1.6.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "e78d4f1cc4ae33bbfc157ed5d5a5ef3bc29227303d595861deb238fcec4e9457"
+
+[[package]]
+name = "itertools"
+version = "0.10.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "a9a9d19fa1e79b6215ff29b9d6880b706147f16e9b1dbb1e4e5947b5b02bc5e3"
+dependencies = [
+ "either",
+]

day3/Cargo.toml

@@ -6,3 +6,4 @@ edition = "2018"
 # See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
 
 [dependencies]
+itertools = "0.10.3"

day3/src/main.rs

@@ -1,3 +1,5 @@
+use itertools::FoldWhile::{Continue, Done};
+use itertools::Itertools;
 use std::{
     fs::File,
     io::{BufRead, BufReader, Lines, Result},
@@ -8,21 +10,83 @@ static INPUT_PATH: &str = "input.txt";
 
 fn main() -> Result<()> {
     let diagnostic_report = read_diagnostic_report(INPUT_PATH)?;
-    let [gamma_rate, epsilon_rate] = extract_report_rates(&diagnostic_report);
+    let [gamma_rate, epsilon_rate, oxygen_rate, co2_rate] =
+        extract_report_rates(&diagnostic_report);
     println!("First puzzle: {}", gamma_rate * epsilon_rate);
+    println!("Second puzzle {}", oxygen_rate * co2_rate);
     Ok(())
 }
 
-fn extract_report_rates(report: &[String]) -> [i32; 2] {
+fn extract_report_rates(report: &[String]) -> [i32; 4] {
     let sums = compute_digits_sums(report);
-    let gamma_rate: String = map_sums(&sums, |&sum| if sum > 0 { "1" } else { "0" }).join("");
+    let gamma_rate = map_sums(&sums, |&sum| if sum > 0 { "1" } else { "0" }).join("");
-    let epsilon_rate: String = map_sums(&sums, |&sum| if sum > 0 { "0" } else { "1" }).join("");
+    let epsilon_rate = map_sums(&sums, |&sum| if sum > 0 { "0" } else { "1" }).join("");
+    let oxygen_rate = filter_report_while(
+        report,
+        |report, iteration| {
+            filter_report_by_nums_bit(report, iteration, |sum, c| {
+                sum >= 0 && c == '1' || sum < 0 && c == '0'
+            })
+        },
+        |report, iteration| report.len() == 1 || iteration > sums.len(),
+    )
+    .first()
+    .unwrap()
+    .clone();
+
+    let co2_rate = filter_report_while(
+        report,
+        |report, iteration| {
+            filter_report_by_nums_bit(report, iteration, |bit_sums, curr_bit| {
+                bit_sums >= 0 && curr_bit == '0' || bit_sums < 0 && curr_bit == '1'
+            })
+        },
+        |report, iteration| report.len() == 1 || iteration > sums.len(),
+    )
+    .first()
+    .unwrap()
+    .clone();
     [
         binary_str_to_int(&gamma_rate),
         binary_str_to_int(&epsilon_rate),
+        binary_str_to_int(&oxygen_rate),
+        binary_str_to_int(&co2_rate),
     ]
 }
 
+fn filter_report_by_nums_bit<T>(report: Vec<String>, bit_index: usize, mut f: T) -> Vec<String>
+where
+    T: FnMut(i32, char) -> bool,
+{
+    let sum = compute_digits_sums(&report)[bit_index];
+    report
+        .into_iter()
+        .filter(|num| {
+            let c = get_char_at_index(num, bit_index);
+            f(sum, c)
+        })
+        .collect()
+}
+
+fn filter_report_while<T, H>(report: &[String], mut f: T, mut w: H) -> Vec<String>
+where
+    T: FnMut(Vec<String>, usize) -> Vec<String>,
+    H: FnMut(&[String], usize) -> bool,
+{
+    (0..)
+        .fold_while(Vec::from(report), |report, index| {
+            if w(&report, index) {
+                return Done(report);
+            }
+            Continue(f(report, index))
+        })
+        .into_inner()
+}
+
+fn get_char_at_index(word: &str, index: usize) -> char {
+    word[index..].chars().next().unwrap()
+}
+
 fn map_sums<T, F>(sums: &[i32], f: F) -> Vec<T>
 where
     F: FnMut(&i32) -> T,