Added day 3 code for part 1 and 2

Signed-off-by: Louis Vallat <louis@louis-vallat.xyz>

day3/Cargo.toml

@@ -0,0 +1,8 @@
+[package]
+name = "day2"
+version = "0.1.0"
+edition = "2021"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]

day3/src/main.rs

@@ -0,0 +1,79 @@
+use std::{fs, env, vec};
+
+
+fn read_input(path: &str) -> String {
+    return fs::read_to_string(path).expect("Cannot read file.");
+}
+
+fn parse_input(s: &str) -> Vec<Vec<u32>> {
+    let mut r: Vec<Vec<u32>> = vec![];
+    for e in s.split("\n") {
+        if !e.is_empty() {
+            r.push(e.chars().filter_map(|e| e.to_digit(2)).collect());
+        }
+    }
+    return r;
+}
+
+fn bit_vec_to_u32(v: &Vec<u32>, invert: bool) -> u32 {
+    let mut acc = 0;
+    for i in 0..v.len() {
+        acc += if invert { (v[i] + 1) % 2 } else { v[i] } << (v.len() - 1 - i);
+    }
+    return acc;
+}
+
+fn get_most_in_col(v: &Vec<Vec<u32>>, c: usize) -> u32 {
+    let mut a = (0, 0);
+    for r in 0..v.len() {
+        if v[r][c] == 0 {
+            a.0 += 1;
+        } else {
+            a.1 += 1;
+        }
+    }
+    if a.1 == a.0 { return 1; }
+    else { return if a.1 > a.0 { 1 } else { 0 }; }
+}
+
+fn get_o2(v: &Vec<Vec<u32>>, c: usize) -> u32 {
+    if v.len() == 1 { return bit_vec_to_u32(&v[0], false); }
+    
+    let a = get_most_in_col(&v, c);
+    let f = v.into_iter().filter(|e| e[c] == (a + 1) % 2)
+        .fold(vec![], |mut acc, e| { acc.push(e.to_owned()); return acc;});
+    return get_o2(&f, c + 1);
+}
+
+fn get_co2(v: &Vec<Vec<u32>>, c: usize) -> u32 {
+    if v.len() == 1 { return bit_vec_to_u32(&v[0], false); }
+    
+    let a = get_most_in_col(&v, c);
+    let f = v.into_iter().filter(|e| e[c] == a)
+        .fold(vec![], |mut acc, e| { acc.push(e.to_owned()); return acc;});
+    return get_co2(&f, c + 1);
+}
+
+fn get_gamma_epsilon(v: &Vec<Vec<u32>>) -> (u32, u32) {
+    let mut acc: Vec<u32> = vec![];
+
+    for c in 0..v[0].len() {
+        acc.push(get_most_in_col(&v, c));
+    }
+    return (bit_vec_to_u32(&acc, false), bit_vec_to_u32(&acc, true));
+}
+
+
+fn main() {
+    let args: Vec<String> = env::args().collect();
+    for arg in args.iter().skip(1) {
+        let v = parse_input(&read_input(&arg));
+        let t = get_gamma_epsilon(&v);
+        let o = get_o2(&v, 0);
+        let c = get_co2(&v, 0);
+        println!("[{}]", arg);
+        println!("\tPart 1 : {} x {} = {}", t.0, t.1, t.0 * t.1);
+        println!("\tPart 2 : {} x {} = {}", o, c, o * c);
+    }
+}
+