Day 17, 65，Valid Number

Valid Number
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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bool isNumber(const char *s) {
    enum InputType {
        INVALID,    // 0
        SPACE,      // 1
        SIGN,       // 2
        DIGIT,      // 3
        DOT,        // 4
        EXPONENT,   // 5
        NUM_INPUTS  // 6
    };
    int transitionTable[][NUM_INPUTS] = {
        -1,  0,  3,  1,  2, -1,     // next states for state 0
        -1,  8, -1,  1,  4,  5,     // next states for state 1
        -1, -1, -1,  4, -1, -1,     // next states for state 2
        -1, -1, -1,  1,  2, -1,     // next states for state 3
        -1,  8, -1,  4, -1,  5,     // next states for state 4
        -1, -1,  6,  7, -1, -1,     // next states for state 5
        -1, -1, -1,  7, -1, -1,     // next states for state 6
        -1,  8, -1,  7, -1, -1,     // next states for state 7
        -1,  8, -1, -1, -1, -1,     // next states for state 8
    };


int state = 0;
while (*s != '\0') {
    InputType inputType = INVALID;
    if (isspace(*s))
        inputType = SPACE;
    else if (*s == '+' || *s == '-')
        inputType = SIGN;
    else if (isdigit(*s))
        inputType = DIGIT;
    else if (*s == '.')
        inputType = DOT;
    else if (*s == 'e' || *s == 'E')
        inputType = EXPONENT;

    // Get next state from current state and input symbol
    state = transitionTable[state][inputType];

    // Invalid input
    if (state == -1) return false;
    else ++s;
}
// If the current state belongs to one of the accepting (final) states,
// then the number is valid
return state == 1 || state == 4 || state == 7 || state == 8;
}