Valid Number
To solve this coding challenge, we need to determine if a given string represents a valid number according to specific rules. The problem can be divided into smaller components, each checking different aspects of the string to ensure it conforms to the criteria for a valid number. Here's a detailed explanation and step-by-step pseudocode to solve the problem.
Explanation
A number can be valid based on the following definitions:-
Integer
: An optional sign (
-
+
-
Decimal
: An optional sign (
-
+
-
Digits followed by a dot (
.
-
Digits followed by a dot (
.
-
A dot (
.
-
Exponent
: Defined with an exponent notation (
e
E
The challenge involves parsing the string to check if it matches these definitions. We will break down the problem into manageable steps:
- Trim : Remove any leading or trailing whitespace.
- Sign : Check for an optional sign at the beginning.
- Digits and Dots : Validate the presence and placement of digits and dots.
-
Exponent
: If an
e
E
Here is the pseudocode:
- Trim Whitespace :
- Strip leading and trailing whitespace.
-
Check if the resultant string is empty, return
false
- Initialize Flags :
-
found_digit
-
found_dot
-
found_exponent
e
E
-
found_digit_after_exponent
- Iterate Over String :
- Loop through each character, updating flags based on character type.
-
For digits, set
found_digit
true
found_digit_after_exponent
true
-
For a dot (
.
-
For an exponent (
e
E
-
For sign characters (
+
-
- Final Validation :
- Ensure at least one digit is present before and after any exponent.
function is_valid_number(s):
# Trim any whitespace from start and end
strip_whitespace_from_edges(s)
# Check if the string is empty after trimming
if s is empty:
return false
# Initialize flags
found_digit = false
found_dot = false
found_exponent = false
found_digit_after_exponent = false
# Define allowed characters
digits = '0123456789'
exponent_chars = 'eE'
sign_chars = '+-'
dot_char = '.'
# Iterate over each character in the string
for each character in s:
if character is in digits:
found_digit = true
if found_exponent:
found_digit_after_exponent = true
elif character == dot_char:
if found_dot or found_exponent:
# Invalid if more than one dot or dot after exponent
return false
found_dot = true
elif character is in exponent_chars:
if found_exponent or not found_digit:
# Invalid if more than one exponent or exponent before any digit
return false
found_exponent = true
found_digit_after_exponent = false # Reset for exponent part
elif character is in sign_chars:
# Sign characters are allowed only at the beginning
# or immediately after an exponent
if s_length_before_current_char_is_not(0_and_previous_char_is_not_in_exponent_chars):
return false
else:
# Any other character is invalid
return false
# Final check: String must contain at least one digit
# and if there's an exponent, it must have a valid number after it
if not found_digit or (found_exponent and not found_digit_after_exponent):
return false
return true