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#![ feature(test, bool_to_option) ]
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extern crate test ;
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use itertools ::Itertools ;
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use std ::env ;
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fn read_input ( ) -> Vec < usize > {
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std ::fs ::read_to_string ( env ::args ( ) . nth ( 1 ) . filter ( | n | n ! = " --bench " ) . unwrap_or ( String ::from ( " inputs/day01 " ) ) )
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. unwrap ( )
. lines ( )
. filter_map ( | l | l . parse ( ) . ok ( ) )
. collect ( )
}
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fn part1 ( input : & [ usize ] ) -> usize {
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input
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. iter ( )
. tuple_combinations ( )
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. find_map ( | ( & a , & b ) | ( a + b = = 2020 ) . then_some ( a * b ) )
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. unwrap ( )
}
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fn part2 ( input : & [ usize ] ) -> usize {
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let mut p2_table = [ None ; 2020 ] ;
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for ( & a , & b ) in input . iter ( ) . tuple_combinations ( ) {
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if a + b < 2020 {
p2_table [ a + b ] = Some ( ( a , b ) )
}
}
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let ( a , b ) = input . iter ( ) . find_map ( | x | p2_table [ 2020 - x ] ) . unwrap ( ) ;
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a * b * ( 2020 - a - b )
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}
fn main ( ) {
let input = read_input ( ) ;
println! ( " Part 1: {} " , part1 ( & input ) ) ;
println! ( " Part 2: {} " , part2 ( & input ) ) ;
}
#[ cfg(test) ]
mod tests {
use super ::* ;
use test ::{ black_box , Bencher } ;
#[ bench ]
fn bench_part1 ( b : & mut Bencher ) {
let input = read_input ( ) ;
b . iter ( | | black_box ( part1 ( black_box ( & input ) ) ) ) ;
}
#[ bench ]
fn bench_part2 ( b : & mut Bencher ) {
let input = read_input ( ) ;
b . iter ( | | black_box ( part2 ( black_box ( & input ) ) ) ) ;
}
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}