LeetCode 65 Valid Number (Python)

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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.

Solution Python


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class Solution:
    # @param s, a string
    # @return a boolean
    def isNumber(self, s):
        ss = s.strip()
        i = 0
        INITIAL = 0
        NUMBER = 1
        DECIMAL = 3
        SCIENTIFIC = 4
        MINUS = 5
        PLUS = 6
        status = INITIAL
        ldecimal = False
        decimal = 0
        scientific = 0
        while True:
            if i == len(ss): break
            if status == INITIAL:
                if ss[i] == '.':
                    status = DECIMAL
                    ldecimal = True
                    decimal += 1
                elif '0' <= ss[i] <= '9':
                    status = NUMBER
                elif ss[i] == '-':
                    status = MINUS
                elif ss[i] == '+':
                    status = PLUS
                else:
                    return False
            elif status == NUMBER:
                if ss[i] == '.':
                    if scientific:
                        return False
                    status = DECIMAL
                    if decimal:
                        return False
                    decimal += 1
                elif '0' <= ss[i] <= '9':
                    pass
                elif ss[i] == 'e':
                    if scientific:
                        return False
                    scientific += 1
                    status = SCIENTIFIC
                else:
                    return False
            elif status == DECIMAL:
                if '0' <= ss[i] <= '9':
                    status = NUMBER
                elif ss[i] == 'e':
                    if ldecimal: return False
                    scientific += 1
                    status = SCIENTIFIC
                else:
                    return False
            elif status == SCIENTIFIC:
                if '0' <= ss[i] <= '9':
                    status = NUMBER
                elif ss[i] == '+':
                    status = PLUS
                elif ss[i] == '-':
                    status = MINUS
                else:
                    return False
            elif status == MINUS:
                if ss[i] == '.':
                    status = DECIMAL
                    ldecimal = True
                    decimal += 1
                elif '0' <= ss[i] <= '9':
                    status = NUMBER
                else:
                    return False
            elif status == PLUS:
                if ss[i] == '.':
                    status = DECIMAL
                    ldecimal = True
                    decimal += 1
                elif '0' <= ss[i] <= '9':
                    status = NUMBER
                else:
                    return False
            else:    
                raise
            i += 1
        if status == NUMBER:
            pass
        elif status == DECIMAL and not ldecimal:
            pass
        else:
            return False
        return True

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