Counting Sundays

2014-09-14

Problem 019: Counting Sundays

Description:

You are given the following information, but you may prefer to do some research for yourself.

1 Jan 1900 was a Monday.
Thirty days has September,
April, June and November.
All the rest have thirty-one,
Saving February alone,
Which has twenty-eight, rain or shine.
And on leap years, twenty-nine.
A leap year occurs on any year evenly divisible by 4, but not on a century unless it is divisible by 400.

How many Sundays fell on the first of the month during the twentieth century (1 Jan 1901 to 31 Dec 2000)?

Solution:

v303232332323
v313232332323
6
>2*>::0g"0"-47*+\0p::v
   |:-1p1\+*74-"0"g1 <
v $<
>202p112p122p"2&"*1+32p092pv
v20+1g20p29+g29!+-1g21%7g20<>#       0# v#   <      >                 >v
>p12g1+12p32g4%             |       >1 >>22g\g12g1--|
                            >32g"d"%|  0^ <  #      >112p22g:1+22p66+-|
                          v%*4"d"g23<>#^_1^  |-+1*"(2"g23<p23+1g23p221<
                          >          ^>1^    >92g.@      ^             <

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Output:

Stack: (0)

Explanation:

In the first two rows we remember the day-count of each month. First row is normal years, second row leap years. Then we just enumerate through all days and test if its a Sunday and the first of month.

Interpreter steps:	3 197 878
Execution time (BefunExec):	546ms (5.86 MHz)
Program size:	72 x 12 (fully conform befunge-93)
Solution:	171
Solved at:	2014-09-14