Valid Number

Desicription

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

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class Solution {
public:
    bool isNumber(string s) {
        int index = 0;
        for(; s[index] == ' '; index++);
        if(s[index] == '+' || s[index] == '-')
            index++;
        int n_num = 0, n_pt = 0;
        for(; ((s[index] <= '9' && s[index] >= '0') || s[index] == '.'); index++)
            s[index] == '.'?n_pt++:n_num++;
        if(!n_num || n_pt > 1)
            return 0;
        if(s[index] == 'e'){
            index++;
            if(s[index] == '+' || s[index] == '-')
                index++;
            int n_num = 0;
            for(; s[index] >= '0' && s[index] <= '9'; index++)
                n_num++;
            if(!n_num)
                return 0;
        }
        for(; s[index] == ' '; index++);
        return !s[index];
    }
};