2023 Day 6

2023/Makefile

@@ -2,7 +2,7 @@ FC:=gfortran
 FFLAGS:=-Wall -Wno-maybe-uninitialized
 BIN:=./bin
 SRC:=./src
-BINS:=./bin/day01.bin ./bin/day01b.bin ./bin/day02.bin ./bin/day03.bin ./bin/day04.bin ./bin/day05.bin ./bin/day05b.bin
+BINS:=./bin/day01.bin ./bin/day01b.bin ./bin/day02.bin ./bin/day03.bin ./bin/day04.bin ./bin/day05.bin ./bin/day05b.bin ./bin/day06.bin
 
 all: aoc19
 

2023/data/day06.txt

@@ -0,0 +1,2 @@
+Time:        42     89     91     89
+Distance:   308   1170   1291   1467

2023/data/day06b.txt

@@ -0,0 +1,2 @@
+Time:     42899189
+Distance: 308117012911467

2023/data/day06ex1.txt

@@ -0,0 +1,2 @@
+Time:      7  15   30
+Distance:  9  40  200

2023/src/day06.f90

@@ -0,0 +1,84 @@
+program day6
+    implicit none
+    integer, parameter :: ikind = selected_int_kind(12)
+    integer, parameter :: max_chars = 300
+    character(200) :: fname
+    character(max_chars) :: fline
+    integer :: n_arguments
+    integer(kind=ikind), allocatable :: times(:)
+    integer(kind=ikind), allocatable :: records(:)
+    integer :: pos_col, n_races, race
+    integer(kind=ikind) :: i, c_over, dist, win_mult = 1
+
+    print *, "Number of bits: ", ikind * 8
+    n_arguments = command_argument_count()
+    if (n_arguments .eq. 1) then
+        call get_command_argument(1, fname)
+        print *, "File: ", trim(fname)
+        print *
+    else
+        print *, "Wrong number of arguments: ", n_arguments
+        stop
+    end if
+
+
+    open(10, file=fname)
+    read(10, "(A)") fline
+    pos_col = scan(fline, ":")
+    n_races = num_ints(fline)
+    allocate(times(1:n_races))
+    allocate(records(1:n_races))
+    print *, "Number of races: ", n_races
+    read(fline((pos_col + 1):max_chars), *) times
+    read(10, "(A)") fline
+    pos_col = scan(fline, ":")
+    read(fline((pos_col + 1):max_chars), *) records
+
+    do race=1,n_races
+        c_over = 0
+        do i=1,times(race)-1
+            dist = i * (times(race) - i)
+            if (dist .gt. records(race)) then
+                c_over = c_over + 1
+            end if
+        end do
+        win_mult = win_mult * c_over
+        write(*, 20) race, c_over
+    end do
+    print *
+    print *, "Tolerance: ", win_mult
+
+20  format("Race: ", i1, ". Ways to win: ", i12)
+
+    contains
+        function num_ints(str)
+            implicit none
+            character(*), intent(in) :: str
+            character(10), parameter :: digits = "0123456789"
+            integer :: num_ints
+            integer :: cur, cur0
+            integer :: str_len
+            cur = 0
+            cur0 = 0
+            num_ints = 0
+            str_len = len_trim(str)
+            do 
+                cur = scan(str((cur + 1):str_len), digits) + cur0
+                if (cur .eq. cur0) then
+                    return
+                end if
+                cur0 = cur
+                num_ints = num_ints + 1
+                if (cur + 1 .ge. str_len) then
+                    return
+                end if
+                cur = verify(str((cur + 1):str_len), digits) + cur0
+                if (cur .eq. cur0) then
+                    return
+                else if (cur + 1 .ge. str_len) then
+                    return
+                end if
+                cur0 = cur
+            end do
+        end function num_ints
+end program day6