Middle three digits
You are encouraged to solve this task according to the task description, using any language you may know.
The task is to:
- “Write a function/procedure/subroutine that is called with an integer value and returns the middle three digits of the integer if possible or a clear indication of an error if this is not possible.”
Your function should be tested with the following values; the first line should return valid answers, those of the second line should return clear indications of an error:
123, 12345, 1234567, 987654321, 10001, -10001, -123, -100, 100, -12345 1, 2, -1, -10, 2002, -2002, 0
Show your output on this page.
D
<lang d>import std.stdio, std.traits, std.math, std.conv;
string middleThreeDigits(T)(in T n) if (isIntegral!T) {
auto s = n.abs().text();
auto len = s.length;
if (len < 3 || len % 2 == 0)
return "Need odd and >= 3 digits";
auto mid = len / 2;
return s[mid - 1 .. mid + 2];
}
void main() {
immutable passing = [123, 12345, 1234567, 987654321, 10001, -10001,
-123, -100, 100, -12345];
immutable failing = [1, 2, -1, -10, 2002, -2002, 0];
foreach (n; passing ~ failing)
writefln("middleThreeDigits(%s): %s", n, middleThreeDigits(n));
}</lang>
middleThreeDigits(123): 123 middleThreeDigits(12345): 234 middleThreeDigits(1234567): 345 middleThreeDigits(987654321): 654 middleThreeDigits(10001): 000 middleThreeDigits(-10001): 000 middleThreeDigits(-123): 123 middleThreeDigits(-100): 100 middleThreeDigits(100): 100 middleThreeDigits(-12345): 234 middleThreeDigits(1): Need odd and >= 3 digits middleThreeDigits(2): Need odd and >= 3 digits middleThreeDigits(-1): Need odd and >= 3 digits middleThreeDigits(-10): Need odd and >= 3 digits middleThreeDigits(2002): Need odd and >= 3 digits middleThreeDigits(-2002): Need odd and >= 3 digits middleThreeDigits(0): Need odd and >= 3 digits
OCaml
<lang ocaml>let even x = (x land 1) <> 1
let middle_three_digits x =
let s = string_of_int (abs x) in let n = String.length s in if n < 3 then failwith "need >= 3 digits" else if even n then failwith "need odd number of digits" else String.sub s (n / 2 - 1) 3
let passing = [123; 12345; 1234567; 987654321; 10001; -10001; -123; -100; 100; -12345] let failing = [1; 2; -1; -10; 2002; -2002; 0]
let print x =
let res = try (middle_three_digits x) with Failure e -> "failure: " ^ e in Printf.printf "%d: %s\n" x res
let () =
print_endline "Should pass:"; List.iter print passing; print_endline "Should fail:"; List.iter print failing;
- </lang>
- Output:
Should pass: 123: 123 12345: 234 1234567: 345 987654321: 654 10001: 000 -10001: 000 -123: 123 -100: 100 100: 100 -12345: 234 Should fail: 1: failure: need >= 3 digits 2: failure: need >= 3 digits -1: failure: need >= 3 digits -10: failure: need >= 3 digits 2002: failure: need odd number of digits -2002: failure: need odd number of digits 0: failure: need >= 3 digits
Perl 6
<lang Perl6>sub middle-three($n) {
given $n.abs {
when .chars < 3 { "$n is too short" }
when .chars %% 2 { "$n has an even number of digits" }
default { "The three middle digits of $n are: ", .substr: (.chars - 3)/2, 3 }
}
}
say middle-three($_) for <
123 12345 1234567 987654321 10001 -10001 -123 -100 100 -12345 1 2 -1 -10 2002 -2002 0
>;</lang>
- Output:
The three middle digits of 123 are: 123 The three middle digits of 12345 are: 234 The three middle digits of 1234567 are: 345 The three middle digits of 987654321 are: 654 The three middle digits of 10001 are: 000 The three middle digits of -10001 are: 000 The three middle digits of -123 are: 123 The three middle digits of -100 are: 100 The three middle digits of 100 are: 100 The three middle digits of -12345 are: 234 1 is too short 2 is too short -1 is too short -10 is too short 2002 has an even number of digits -2002 has an even number of digits 0 is too short
Python
<lang python>>>> def middle_three_digits(i): s = str(abs(i)) length = len(s) assert length >= 3 and length % 2 == 1, "Need odd and >= 3 digits" mid = length // 2 return s[mid-1:mid+2]
>>> passing = [123, 12345, 1234567, 987654321, 10001, -10001, -123, -100, 100, -12345] >>> failing = [1, 2, -1, -10, 2002, -2002, 0] >>> for x in passing + failing: try: answer = middle_three_digits(x) except AssertionError as error: answer = error print("middle_three_digits(%s) returned: %r" % (x, answer))
middle_three_digits(123) returned: '123'
middle_three_digits(12345) returned: '234'
middle_three_digits(1234567) returned: '345'
middle_three_digits(987654321) returned: '654'
middle_three_digits(10001) returned: '000'
middle_three_digits(-10001) returned: '000'
middle_three_digits(-123) returned: '123'
middle_three_digits(-100) returned: '100'
middle_three_digits(100) returned: '100'
middle_three_digits(-12345) returned: '234'
middle_three_digits(1) returned: AssertionError('Need odd and >= 3 digits',)
middle_three_digits(2) returned: AssertionError('Need odd and >= 3 digits',)
middle_three_digits(-1) returned: AssertionError('Need odd and >= 3 digits',)
middle_three_digits(-10) returned: AssertionError('Need odd and >= 3 digits',)
middle_three_digits(2002) returned: AssertionError('Need odd and >= 3 digits',)
middle_three_digits(-2002) returned: AssertionError('Need odd and >= 3 digits',)
middle_three_digits(0) returned: AssertionError('Need odd and >= 3 digits',)
>>> </lang>
XPL0
<lang XPL0>include c:\cxpl\stdlib;
func Mid3Digits(I); \Return the middle three digits of I int I; int Len, Mid; char S(10); [ItoA(abs(I), S); Len:= StrLen(S); if Len<3 or (Len&1)=0 then return "Must be 3, 5, 7 or 9 digits"; Mid:= Len/2; S:= S + Mid - 1; S(2):= S(2) ! $80; \terminate string return S; \WARNING: very temporary ];
int Passing, Failing, X; [Passing:= [123, 12345, 1234567, 987654321, 10001, -10001, -123, -100, 100, -12345];
Failing:= [1, 2, -1, -10, 2002, -2002, 0]; \WARNING: nasty trick
for X:= 0 to 16 do
[Text(0, "Middle three digits of "); IntOut(0, Passing(X));
Text(0, " returned: ");
Text(0, Mid3Digits(Passing(X))); CrLf(0);
];
]</lang>
- Output:
Middle three digits of 123 returned: 123 Middle three digits of 12345 returned: 234 Middle three digits of 1234567 returned: 345 Middle three digits of 987654321 returned: 654 Middle three digits of 10001 returned: 000 Middle three digits of -10001 returned: 000 Middle three digits of -123 returned: 123 Middle three digits of -100 returned: 100 Middle three digits of 100 returned: 100 Middle three digits of -12345 returned: 234 Middle three digits of 1 returned: Must be 3, 5, 7 or 9 digits Middle three digits of 2 returned: Must be 3, 5, 7 or 9 digits Middle three digits of -1 returned: Must be 3, 5, 7 or 9 digits Middle three digits of -10 returned: Must be 3, 5, 7 or 9 digits Middle three digits of 2002 returned: Must be 3, 5, 7 or 9 digits Middle three digits of -2002 returned: Must be 3, 5, 7 or 9 digits Middle three digits of 0 returned: Must be 3, 5, 7 or 9 digits