[LeetCode] Valid Number 确认是否为数值

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.

click to show spoilers.

Update (2014-12-06):
New test cases had been added. Thanks unfounder‘s contribution.

1. 输入前置空格
2. 正负号
3. 连续的数值，包括‘.’
4. 符号e
5. 正负号
6. 连续数值，不包括‘.‘
7. 后续空格

按上面的规则便行。

#include <iostream>
using namespace std;

class Solution {
public:
    bool isNumber(const char *s)
    {
        int idx =0;
        for(;s[idx]==‘ ‘;idx++);
        if(s[idx]==‘-‘||s[idx]==‘+‘)    idx++;
        int Point=0,Num=0;
        for(;(s[idx]>=‘0‘&&s[idx]<=‘9‘)||s[idx]==‘.‘;idx++)
            s[idx]==‘.‘?Point++:Num++;
        if(Point>1||Num<1)  return false;
        if(s[idx]==‘e‘){
            idx++;
            if(s[idx]==‘-‘||s[idx]==‘+‘)    idx++;
            Num=0;
            for(;s[idx]>=‘0‘&&s[idx]<=‘9‘;idx++)    Num++;
            if(Num<1)   return false;
        }
        for(;s[idx]==‘ ‘;idx++);
        return s[idx]==‘\0‘;
    }
};

int main()
{
    char a[]="-e-";
    Solution sol;
    cout<<sol.isNumber(a)<<endl;
    return 0;
}