day1.rs

day1.rs

use std::fs::File;
use std::io::{self, BufRead};
use std::path::Path;
use std::str::FromStr;

fn main() {
    let mut calories: Vec<u64> = Vec::new();
    let mut caloriesum = 0;
    let mut maxcalories = 0;
    // File hosts must exist in current path before this produces output
    if let Ok(lines) = read_lines("./input") {
        // Consumes the iterator, returns an (Optional) String

        for line in lines {
            if let Ok(ip) = line {
                if let Ok(cals) = u32::from_str(&ip) {
                    //println!("found a number");
                    caloriesum += cals;
                } else {
                    if caloriesum > maxcalories { 
                        maxcalories = caloriesum;
                    };
                    calories.push(caloriesum as u64);
                    caloriesum = 0;
                }
            } 
        }
    }
    if caloriesum > maxcalories {
        maxcalories = caloriesum;
    }
    calories.push(caloriesum as u64);
    println!("{:?}", calories);
    println!("Max calories {}", maxcalories);

    let elfnumber = calories.iter().position(|&x| x == maxcalories as u64);
    println!("elf number: {}", elfnumber.unwrap());
    //End of part one of the challenge. For part 2 we start with the vec of calories, need to find
    //the top 3
    //
    calories.sort();
    
    let top3:u64 = calories.iter().rev().take(3).sum();
    println!("top 3 {}", top3);


}

// The output is wrapped in a Result to allow matching on errors
// Returns an Iterator to the Reader of the lines of the file.
fn read_lines<P>(filename: P) -> io::Result<io::Lines<io::BufReader<File>>>
where P: AsRef<Path>, {
    let file = File::open(filename)?;
    Ok(io::BufReader::new(file).lines())
}