add day03

day03/Cargo.lock

@@ -0,0 +1,7 @@
+# This file is automatically @generated by Cargo.
+# It is not intended for manual editing.
+version = 3
+
+[[package]]
+name = "day3"
+version = "0.1.0"

day03/Cargo.toml

@@ -0,0 +1,8 @@
+[package]
+name = "day3"
+version = "0.1.0"
+edition = "2021"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]

day03/src/main.rs

@@ -0,0 +1,31 @@
+use std::fs;
+
+const MAX_BITS: usize = 12;
+
+fn main() {
+    let mut true_count: [ u16 ; MAX_BITS ] = [ 0 ; MAX_BITS ];
+    let mut line_count: u16 = 0;
+    let data = fs::read_to_string("./data/input").expect("Unable to read file");
+
+    for line in data.lines() {
+        let str_rev: String = line.chars().rev().collect();
+        for (pos, chr) in str_rev.chars().enumerate() {
+            if chr == '1' { 
+                true_count[pos] += 1 
+            }
+        }
+        line_count += 1;
+    }
+
+    let even_count = line_count / 2;
+    let mut gamma: u32 = 0;
+    let mut epsilon: u32 = 0;
+    for (pos, true_count) in true_count.iter_mut().enumerate() {
+        if *true_count > even_count {
+            gamma += (2 as u32).pow(pos as u32);
+        } else {
+            epsilon += (2 as u32).pow(pos as u32);
+        }
+    }
+    println!("power consumption {}", epsilon * gamma)
+}