class Solution {
public boolean isNumber(String s) {
s = s.trim();
char[] ch = s.toCharArray();
int idx = 0;
int n = ch.length;
boolean signFound = false;
boolean decimalFound = false;
boolean numFound = false;
boolean expoFound = false;
while (idx < n) {
if (ch[idx] == '+' || ch[idx] == '-') {
if (numFound || signFound || decimalFound) {
return false;
}
signFound = true;
}
else if (ch[idx] == '.') {
if (decimalFound) {
return false;
}
decimalFound = true;
}
else if (Character.isLetter(ch[idx])) {
if (ch[idx] == 'e') {
if (!numFound) {
return false;
}
idx++;
expoFound = true;
break;
}
else {
return false;
}
}
else if (Character.isDigit(ch[idx])) {
numFound = true;
}
else if (ch[idx] == ' ') {
if (numFound || signFound || decimalFound) {
return false;
}
}
idx++;
}
if (!numFound) {
return false;
}
if (expoFound && idx == n) {
return false;
}
signFound = false;
numFound = false;
while (idx < n) {
if (ch[idx] == '.') {
return false;
}
else if (ch[idx] == '+' || ch[idx] == '-') {
if (signFound) {
return false;
}
if (numFound) {
return false;
}
signFound = true;
}
else if (Character.isDigit(ch[idx])) {
numFound = true;
}
else {
return false;
}
idx++;
}
if (expoFound && !numFound) {
return false;
}
return true;
}
}