Valid Number
Validate if a given string can be interpreted as a decimal number.
Some examples:
"0"
=> true
" 0.1 "
=> true
"abc"
=> false
"1 a"
=> false
"2e10"
=> true
" -90e3 "
=> true
" 1e"
=> false
"e3"
=> false
" 6e-1"
=> true
" 99e2.5 "
=> false
"53.5e93"
=> true
" --6 "
=> false
"-+3"
=> false
"95a54e53"
=> false
Note: It is intended for the problem statement to be ambiguous. You should gather all requirements up front before implementing one. However, here is a list of characters that can be in a valid decimal number:
Numbers 0-9
Exponent - "e"
Positive/negative sign - "+"/"-"
Decimal point - "."
Of course, the context of these characters also matters in the input.
class Solution {
public boolean isNumber(String s) {
s = s.trim();
boolean pointSeen = false;
boolean eSeen = false;
boolean numberSeen = false;
for (int i = 0; i < s.length(); i++) {
if ('0' <= s.charAt(i) && s.charAt(i) <= '9')
numberSeen = true;
else if (s.charAt(i) == '.') {
if (eSeen || pointSeen)
return false;
pointSeen = true;
} else if (s.charAt(i) == 'e') {
if (eSeen || !numberSeen)
return false;
numberSeen = false;
eSeen = true;
} else if (s.charAt(i) == '-' || s.charAt(i) == '+') {
if (i != 0 && s.charAt(i - 1) != 'e')
return false;
} else
return false;
}
return numberSeen;
}
}
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