Valid Number

最新推荐文章于 2021-02-12 17:55:35 发布

原创最新推荐文章于 2021-02-12 17:55:35 发布 · 356 阅读

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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.

class Solution:
    # @param s, a string
    # @return a boolean
    def isNumber(self, s):
        
        INVALID=0; SPACE=1; SIGN=2; DIGIT=3; DOT=4; EXPONENT=5;
        transitionTable=[[-1,  0,  3,  1,  2, -1],    #0 no input or just spaces 
                         [-1,  8, -1,  1,  4,  5],    #1 input is digits 
                         [-1, -1, -1,  4, -1, -1],    #2 no digits in front just Dot 
                         [-1, -1, -1,  1,  2, -1],    #3 sign 
                         [-1,  8, -1,  4, -1,  5],    #4 digits and dot in front 
                         [-1, -1,  6,  7, -1, -1],    #5 input 'e' or 'E' 
                         [-1, -1, -1,  7, -1, -1],    #6 after 'e' input sign 
                         [-1,  8, -1,  7, -1, -1],    #7 after 'e' input digits 
                         [-1,  8, -1, -1, -1, -1]]    #8 after valid input input space
        state=0; i=0
        while i < len(s) :
            inputtype = INVALID
            if s[i] ==' ' : inputtype = SPACE
            elif s[i] == '+' or s[i] == '-' : inputtype = SIGN
            elif s[i] in '0123456789' : inputtype = DIGIT
            elif s[i] == '.' : inputtype = DOT
            elif s[i] == 'e' or s[i] == 'E': inputtype = EXPONENT
            state = transitionTable[state][inputtype]
            if state == -1 : return False
            i += 1
        return state == 1 or state == 4 or state == 7 or state == 8