LeetCode: Valid Number

leetcode里最恶心的题目。。面试问这种题目可以去撞墙了。。

 自己写了一遍

class Solution {
public:
    bool isNumber(const char *s) {
        // Start typing your C/C++ solution below
        // DO NOT write int main() function
        while (isspace(*s)) s++;
        if (*s == '+' || *s == '-') s++;
        bool space, e, dot, first, second;
        space = e = dot = first = second = false;
        while (*s != '\0') {
            if (*s == '.') {
                if (e || space || dot || second) return false;
                dot = true;
            }
            else if (*s == 'e') {
                if (e || space || !first) return false;
                e = true;
            }
            else if (isdigit(*s)) {
                if (space) return false;
                if (!e) first = true;
                else second = true;
            }
            else if (isspace(*s)) space = true;
            else if (*s == '+' || *s == '-') {
                if (space || *(s-1) != 'e') return false;
            }
            else return false;
            s++;
        }
        if (!first) return false;
        if (e && !second) return false;
        return true;
    }
};

 C#

public class Solution {
    public bool IsNumber(string s) {
        int cur = 0;
        while (cur < s.Length && s[cur] == ' ') cur++;
        if (cur < s.Length && (s[cur] == '+' || s[cur] == '-')) cur++;
        bool space, e, dot, first, second;
        space = e = dot = first = second = false;
        while (cur < s.Length) {
            if (s[cur] == '.') {
                if (e || space || dot || second) return false;
                dot = true;
            }
            else if (s[cur] == 'e') {
                if (e || space || !first) return false;
                e = true;
            }
            else if (s[cur] >= '0' && s[cur] <= '9') {
                if (space) return false;
                if (!e) first = true;
                else second = true;
            }
            else if (s[cur] == ' ') space = true;
            else if (s[cur] == '+' || s[cur] == '-') {
                if (space || (cur > 0 && s[cur-1] != 'e')) return false;
            }
            else return false;
            cur++;
        }
        if (!first) return false;
        if (e && !second) return false;
        return true;
    }
}