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#![ feature(core_intrinsics) ]
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#![ feature(test) ]
extern crate test ;
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use std ::{ intrinsics ::unlikely , ops ::RangeInclusive } ;
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type TargetArea = ( RangeInclusive < isize > , RangeInclusive < isize > ) ;
type Probe = ( ( isize , isize ) , ( isize , isize ) ) ;
#[ derive(Debug, PartialEq) ]
enum ProbeStatus {
Hit ,
Miss ,
NoLongerReachable ,
}
fn calc_status ( ( _ , ( x , y ) ) : & Probe , ( xtarget , ytarget ) : & TargetArea ) -> ProbeStatus {
if xtarget . contains ( x ) & & ytarget . contains ( y ) {
ProbeStatus ::Hit
} else if y < ytarget . start ( ) {
ProbeStatus ::NoLongerReachable
} else {
ProbeStatus ::Miss
}
}
fn parse_input ( ) -> TargetArea {
( 34 ..= 67 , - 215 ..= - 186 )
}
fn step ( ( ( xvel , yvel ) , ( x , y ) ) : Probe ) -> Probe {
( ( xvel - xvel . signum ( ) , yvel - 1 ) , ( x + xvel , y + yvel ) )
}
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fn part1 ( hits : & Vec < ( ( isize , isize ) , isize ) > ) -> isize {
* hits . iter ( ) . map ( | ( _ , y ) | y ) . max ( ) . unwrap ( )
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}
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fn find_hits ( target : & TargetArea ) -> Vec < ( ( isize , isize ) , isize ) > {
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( 1 ..= * target . 0. end ( ) )
. flat_map ( move | x | ( * target . 1. start ( ) .. 250 ) . map ( move | y | ( x , y ) ) )
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. filter_map ( | ( xstart , ystart ) | {
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let mut probe = ( ( xstart , ystart ) , ( 0 , 0 ) ) ;
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let mut y_high = 0 ;
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loop {
probe = step ( probe ) ;
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if unlikely ( probe . 0 . 1 = = 0 ) {
y_high = probe . 1 . 1 ;
}
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match calc_status ( & probe , target ) {
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ProbeStatus ::Hit = > return Some ( ( ( xstart , ystart ) , y_high ) ) ,
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ProbeStatus ::Miss = > ( ) ,
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ProbeStatus ::NoLongerReachable = > return None ,
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}
}
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} )
. collect ( )
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}
fn main ( ) {
let target = parse_input ( ) ;
let hits = find_hits ( & target ) ;
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println! ( " Part 1: {} " , part1 ( & hits ) ) ;
println! ( " Part 2: {} " , hits . len ( ) ) ;
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}
#[ cfg(test) ]
mod tests {
use super ::* ;
use aoc2021 ::* ;
#[ test ]
fn part1_test ( ) {
let input = ( 20 ..= 30 , - 10 ..= - 5 ) ;
let hits = find_hits ( & input ) ;
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assert_eq! ( part1 ( & hits ) , 45 ) ;
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}
#[ test ]
fn part2_test ( ) {
let input = ( 20 ..= 30 , - 10 ..= - 5 ) ;
let hits = find_hits ( & input ) ;
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assert_eq! ( hits . len ( ) , 112 ) ;
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}
#[ bench ]
fn bench_find_hits ( b : & mut test ::Bencher ) {
let input = parse_input ( ) ;
b . iter ( | | assert_eq! ( find_hits ( & input ) . len ( ) , 2040 ) )
}
#[ bench ]
fn bench_part1 ( b : & mut test ::Bencher ) {
let input = parse_input ( ) ;
let hits = find_hits ( & input ) ;
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b . iter ( | | assert_eq! ( part1 ( & hits ) , 23005 ) )
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}
}