Validate if a given string is numeric.
Some examples:
"0" => true
" 0.1 " => true
"abc" => false
"1 a" => false
"2e10" => true
Note: It is intended for the problem statement to be ambiguous. You should gather all requirements up front before implementing one.
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代码语言：javascript复制 public boolean isNumber(String s) {
if (s == null || s.length() == 0) {
return false;
}
char[] chars = s.toCharArray();
int start = 0, end = chars.length - 1;
// 除去前后的空格
while ((start < end) && chars[start] == ' ') {
start ;
}
while ((start < end) && chars[end] == ' ') {
end--;
}
// 因为while的循环条件是start < end，s为空格时，会剩下一个空格
if (chars[start] == ' ') {
return false;
}
boolean dot = false;
boolean num = false;
boolean ex = false;
for (int i = start; i <= end; i ) {
char c = chars[i];
if (c >= '0' && c <= '9') {
num = true;
} else if (c == 'e') {
if (ex)
return false;
if (!num)
return false;
ex = true;
num = false;
dot = false;
} else if (c == '.') {
if (dot) {
return false;
}
if (ex) {
return false;
}
dot = true;
} else if (c == ' ' || c == '-') {
if (num || dot) {
return false;
}
} else {
return false;
}
}
return num;
}
