Description:
Validate if a given string is numeric.
Example
"0" => true" 0.1 " => true"abc" => false"1 a" => false"2e10" => true
Solution:
class Solution {
public:
/**
* @param s the string that represents a number
* @return whether the string is a valid number
*/
bool isNumber(string& s) {
enum InputType {
SPACE, // 0
SIGN, // 1
DIGIT, // 2
DOT, // 3
EXPONENT, // 4
TYPE_SIZE // 5
};
const int table[][TYPE_SIZE] = {
0, 3, 1, 2, -1,
8, -1, 1, 4, 5,
-1, -1, 4, -1, -1,
-1, -1, 1, 2, -1,
8, -1, 4, -1, 5,
-1, 6, 7, -1, -1,
-1, -1, 7, -1, -1,
8, -1, 7, -1, -1,
8, -1, -1, -1, -1,
};
int state = 0;
for (auto ch : s) {
int inputType;
if (ch == ' ' || ch == '\t')
inputType = SPACE;
else if (ch == '+' || ch == '-')
inputType = SIGN;
else if (ch >= '0' && ch <= '9')
inputType = DIGIT;
else if (ch == '.')
inputType = DOT;
else if (ch == 'e' || ch == 'E')
inputType = EXPONENT;
else return false;
state = table[state][inputType];
if (state == -1) return false;
}
return state == 1 || state == 4 || state == 7 || state == 8;
}
};
转载于:https://www.cnblogs.com/deofly/p/valid-number.html
