Comments on: Boost library rocks!

By: RichB

RichB — Sat, 29 Dec 2007 14:24:21 +0000

Correction: That’s not a Zellers Congruence algorithm. It’s from Tomohiko Sakamoto - see comp.lang.c faq for details.

By: RichB

RichB — Sat, 29 Dec 2007 14:06:02 +0000

JavaScript version using Zeller’s Congruence (doesn’t anyone read the comp.lang.c FAQ nowadays?). I haven’t timed it, but it’s on the order of milliseconds:

window.Zeller={};

Zeller.getDayOfWeek = function(y, m, d) {
var t = [0,3,2,5,0,3,5,1,4,6,2,4];
y-=m<3;
return (y+Math.floor(y/4)-Math.floor(y/100)+Math.floor(y/400)+t[m-1]+d)%7;
}

var sundayCount=0;

for(var i=1901; i<=2000; i++) {
for(var j=1; j<=12; j++) {
if(Zeller.getDayOfWeek(i, j, 1)==0) {
sundayCount++;
}
}
}
document.write(”Number of sundays between 1901-01-01 and 2000-12-31 is ” + sundayCount);

By: depesz

depesz — Fri, 28 Dec 2007 11:54:54 +0000

hmm - there should be *3* spaces in sed. i dont know how to add them in comment box. but it should be like:
sed ’s/XXX/\n/g’
where “X” is space.

By: depesz

depesz — Fri, 28 Dec 2007 11:12:04 +0000

this version of shell should be a bit faster:

for a in `seq 1901 2000`; do cal $a; done | sed ’s/ /\n/g’ | grep -c ‘^ 1 2 3 4 5 6 7′

By: Yacin

Yacin — Fri, 28 Dec 2007 04:04:23 +0000

Ugh, it messes up the spaces, this one actually works

for i in `seq 1 12` ; do for j in `seq 1901 2000`; do cal $i $j | sed ’s/ //g’ | grep 1234567 ; done; done | wc -l

By: Yacin

Yacin — Fri, 28 Dec 2007 03:45:21 +0000

for i in `seq 1 12` ; do for j in `seq 1901 2000`; do cal $i $j | grep " 1 2 3 4 5 6 7"; done; done | wc -l

fixt