Teaching and learning resources • Re: Advent of Code 2024

Code:

$ time chpl --fast --local --launcher smp day18.chpl36.97user 1.28system 0:38.23elapsed 100%CPU (0avgtext+0avgdata 0maxresident)k0inputs+0outputs (0major+0minor)pagefaults 0swaps$ ./day18 -nl1 # Pi 4B at 1500 MHzAdvent of Code 2024 Day 18 RAM RunPart 1 It takes 246 steps to reach the exitPart 2 The blocking block is 22,50Total execution time 0.524505 seconds.

Code:

/*  Advent of Code 2024 Day 18 RAM Run    Written 2025 by Eric Olson    Dedicated to the dog developer.  */use IO,Time,List;type byte=uint(8);const dirs=[(0,1),(-1,0),(0,-1),(1,0)];proc check(ref i:int,ref s:bytes,const p:bytes):bool {    if s.size<i+p.size {        return false;    }    for k in 0..<p.size {        if s[k+i]!=p[k] {            return false;        }    }    i+=p.size;    return true;}proc scanint(ref i:int,ref s:bytes):int {    const d0=b"0"[0],d9=b"9"[0],minus=b"-"[0];    var r=0,iold=i,m=-1;    while i<s.size {        var d=s[i];        if iold==i&&d==minus {            m=1;        } else if d>=d0 && d<=d9 {            r=r*10-(d-d0);        } else {            break;        }        i+=1;    }    return m*r;}proc getpos(ref s:bytes):(int,int) {    var i=0;    var iold=i;    var x=scanint(i,s);    if iold==i {        writeln("Can't find x coordinate in ",s);        exit(1);    }    if !check(i,s,b",") {        writeln("Can't find separator in ",s);        exit(1);    }    iold=i;    var y=scanint(i,s);    if iold==i {        writeln("Can't find y coordinate in ",s);        exit(1);    }    return (x,y);}proc relax(ref board:[]int):int {    var r=0;    for p in board.domain {        for dp in dirs {            var q=p+dp;            if board.domain.contains(q) {                if board[q]<0 {                    continue;                }                if board[q]+1<board[p] {                    board[p]=board[q]+1;                    r+=1;                }            }        }    }    return r;}proc findpath(ref corrupt:list((int,int)),M,N,cm:int):int {    var board:[0..M,0..N]int;    for (i,j) in {0..M,0..N} {        board[i,j]=(M+1)*(N+1);    }    var c=0;    for p in corrupt {        c+=1;        if c>cm {            break;        }        board[p]=-1;    }    board[0,0]=0;    while relax(board) {};    if board[M,N]<(M+1)*(N+1) {        return board[M,N];    }    return max(int);}proc part1(ref corrupt:list((int,int)),M,N,cm:int):int {    return findpath(corrupt,M,N,cm);}proc part2(ref corrupt:list((int,int)),M,N,cm:int):(int,int) {    var a=cm; var b=corrupt.size;    var cold=0,c=(a+b)/2;    while cold!=c {        var fc=findpath(corrupt,M,N,c);        if fc==max(int) {            b=c;        } else {            a=c;        }        cold=c;        c=(a+b)/2;    }    return corrupt(b-1);}proc dowork(){    var io=open("day18.txt",ioMode.r);    var fp=io.reader(locking=false);    var corrupt:list((int,int));    var s:bytes;    while fp.readLine(s,stripNewline=true) {        var (x,y)=getpos(s);        corrupt.pushBack((x,y));    }    var M=0,N=0;    for (x,y) in corrupt {        if M<x {            M=x;        }        if N<y {            N=y;        }    }    var cm=1024;    if M<10 {        cm=12;    }    var p1=part1(corrupt,M,N,cm);    writef("Part 1 It takes %i steps to reach the exit\n",p1);    var p2=part2(corrupt,M,N,cm);    writef("Part 2 The blocking block is %i,%i\n",p2(0),p2(1));}proc main(){    var t:stopwatch;    t.start();    writeln("Advent of Code 2024 Day 18 RAM Run\n");    dowork();    t.stop();    writeln("\nTotal execution time ",t.elapsed()," seconds.");}