LeetCode – Refresh – Valid Number

Logic is tricky. Redo it.

class Solution {
public:
    bool isNumber(string s) {
        int start = 0, end = s.size()-1;
        if (end == -1) return false;
        while (start <= end && s[start] == ' ') start++;
        while (end >= start && s[end] == ' ') end--;
        bool dotflag = false, expflag = false, numflag = false;
        for (int i = start; i <= end; i++) {
            if (s[i] >= '0' && s[i] <= '9') {
                numflag = true;
            } else if (s[i] == 'e') {
                if (expflag || !numflag) return false;
                expflag = true, numflag = false;
            } else if (s[i] == '.') {
                if (dotflag || expflag) return false;
                dotflag = true;
            } else if (s[i] == '+' || s[i] == '-') {
                if (i > start && s[i-1] != 'e') return false;
            } else return false;
        }
        return numflag;
    }
};