coderloop: src/collatz.f comparison

initial committ

comparison

equal deleted inserted replaced

--1:000000000000
+:307a81e46071
+program collatz
+implicit none
+character (len = 100) :: file_name
+integer, parameter :: big = selected_int_kind(11)
+integer  :: n
+call getarg( 1, file_name )
+OPEN(unit = 7, file = file_name)
+read (7,*) n
+write (unit = *, fmt = "(I0)") search_collatz(n)
+contains
+function collatz_next (n) result (r)
+implicit none
+integer (kind = big)  :: r,n
+if (0 == mod(n,2)) then
+r = n/2
+else
+r = 1 + 3*n
+end if
+end function collatz_next
+function collatz_length (n) result (r)
+implicit none
+integer (kind = big)  :: t
+integer :: n,r
+r = 1
+t = n
+do
+if (1 == t) then
+exit
+end if
+r = r + 1
+t = collatz_next(t)
+end do
+end function collatz_length
+function search_collatz (n) result (r)
+implicit none
+integer n,r,i,max,max_val,temp_val
+integer (kind = big) :: t
+t = n
+do i = 1,n-1
+temp_val = collatz_length(i)
+if (temp_val > max_val) then
+max = i
+max_val = temp_val
+end if
+end do
+r = max
+end function search_collatz
+end program collatz

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