In this Leetcode Valid Number Problem Solution A valid number can be split up into these components (in order):
A decimal number or an integer.
(Optional) An 'e' or 'E', followed by an integer.
A decimal number can be split up into these components (in order):
(Optional) A sign character (either '+' or '-').
One of the following formats:
One or more digits, followed by a dot '.'.
One or more digits, followed by a dot '.', followed by one or more digits.
A dot '.', followed by one or more digits.
An integer can be split up into these components (in order):
(Optional) A sign character (either '+' or '-').
One or more digits.
For example, all the following are valid numbers: ["2", "0089", "-0.1", "+3.14", "4.", "-.9", "2e10", "-90E3", "3e+7", "+6e-1", "53.5e93", "-123.456e789"], while the following are not valid numbers: ["abc", "1a", "1e", "e3", "99e2.5", "--6", "-+3", "95a54e53"].
Given a string s, return true if s is a valid number.
Problem solution in Python.
class Solution:
# @param s, a string
# @return a boolean
def isNumber(self, s):
try:
float(s)
return True
except:
return FalseProblem solution in Java.
class Solution
{
public boolean isNumber(String s)
{
if (s == null || s.length() == 0) return false;
s = s.trim();
int i = s.indexOf('e');
if (i == -1)
{
return valid_float_sign(s);
}
return valid_float_sign(s.substring(0, i))
&& valid_int_sign(s.substring(i + 1));
}
// number is like: +3.8
boolean valid_float_sign(String s)
{
if (s.length() == 0) return false;
int i = 0;
if (s.charAt(i) == '+' || s.charAt(i) == '-')
{
++i;
}
return valid_float(s.substring(i));
}
// number is like: 3.8
boolean valid_float(String s)
{
int i = s.indexOf('.');
if (i == -1)
{
return valid_int(s);
}
String left = s.substring(0, i);
String right = s.substring(i + 1);
if (left.length() == 0) return valid_int(right);
if (right.length() == 0) return valid_int(left);
return valid_int(left) && valid_int(right);
}
// number is like: -3
boolean valid_int_sign(String s)
{
if (s.length() == 0) return false;
int i = 0;
if (s.charAt(i) == '+' || s.charAt(i) == '-')
{
++i;
}
return valid_int(s.substring(i));
}
// number is like: 3
boolean valid_int(String s)
{
if (s.length() == 0) return false;
for (int i = 0; i < s.length(); ++i)
{
if (s.charAt(i) >= '0' && s.charAt(i) <= '9')
{
continue;
}
else return false;
}
return true;
}
}Problem solution in C++.
class Solution {
public:
bool isNumber(string s) {
int i, cnt=0, pos;
string s1="", s2="";
bool sign=false, exp=false;
s=regex_replace(s, regex("^ +"), "");
s=regex_replace(s, regex(" +$"), "");
if(!s.size())
return false;
if(s[0]=='-' || s[0]=='+')
s=s.substr(1);
if(s.size()==1 && (s[0]=='.' || s[0]=='+' || s[0]=='-'))
return false;
if(s[s.size()-1]=='e' || s[s.size()-1]=='+' || s[s.size()-1]=='-')
return false;
for(i=0; i<s.size(); i++){
if(s[i]=='.')
cnt++;
if(cnt>1)
return false;
}
cnt=0;
pos=s.find(".");
if(pos!=string::npos){
s1=s.substr(0, pos);
s2=s.substr(pos+1);
}
else s2=s;
if(!s1.size() && s2[0]=='e')
return false;
for(i=0; i<s1.size(); i++){
if(int(s1[i])<48 || int(s1[i])>57)
return false;
}
for(i=0; i<s2.size(); i++){
if(int(s2[i])<48 || int(s2[i])>57){
if(s2[i]!='+' && s2[i]!='-' && s2[i]!='e')
return false;
if(s2[i]=='+' || s2[i]=='-'){
if(sign)
return false;
sign=true;
}
if(s2[i]=='e'){
if(exp)
return false;
exp=true;
}
if(!exp && sign)
return false;
else if(exp && sign)
sign=true;
}
}
return true;
}
};Problem solution in C.
bool isNumber(char *s){
int i;
int counter_sign = 0, counter_e = 0, counter_point = 0, counter_digit = 0, space_in_str = 0;
char previous_c = '\0', c;
int state = 1;
for (i = 0; (c = s[i]) != '\0'; i++) {
int is_sign = 0, is_e = 0, is_point = 0;
if (c == '+' || c == '-'){
is_sign = 1;
}
if (isdigit(c)){
counter_digit++;
}
if (c == 'e'){
is_e = 1;
}
if (c == '.'){
is_point = 1;
}
if (is_sign == 1){
if (( previous_c != '\0' && previous_c != ' ' && previous_c != 'e') || counter_sign >= 2 || previous_c == '.'){
state = 0;
break;
} else {
counter_sign++;
}
}
if (is_point == 1){
if ((!isdigit(previous_c) && previous_c != '\0' && previous_c != ' ' && previous_c != '+' && previous_c != '-') || counter_point >= 1 || (counter_point == 0 && counter_e >= 1)){
state = 0;
break;
} else {
counter_point++;
}
}
if (is_e == 1){
if ((!isdigit(previous_c) && previous_c != '.') || counter_e >= 1 || (previous_c == '.' && counter_digit == 0)){
state = 0;
break;
} else {
counter_e++;
}
}
if (c > '9' && c != 'e') {
state = 0;
break;
}
if (c == ' ' && previous_c != ' ' && previous_c != '\0'){
space_in_str = 1;
}
if (c != ' ' && space_in_str == 1){
state = 0;
break;
}
if (c == ' ' && previous_c == 'e'){
state = 0;
break;
}
previous_c = c;
}
if ((!isdigit(previous_c) && previous_c != ' ' && previous_c != '.')|| (counter_digit == 0)){
state = 0;
}
if (state == 1){
return true;
} else {
return false;
}
}
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