Valid Number.cpp

class Solution {
public:
    bool isNumber(string s) {
        vector<vector<int>> transferTable = {
            {1, 2, 3, -1, -1},
            {-1, 2, 3, -1, -1},
            {-1, 2, 4, 5, -1}, 
            {-1, 4, -1, -1, -1},
            {-1, 4, -1, 5, -1},
            {6, 7, -1, -1, -1},
            {-1, 7, -1, -1, -1},
            {-1, 7, -1, -1, -1}
        };
        
        int state = 0, len = s.size(), i = 0, j = len - 1;
        while(i < len && s[i] == ' ')++i;
        while(j >= 0 && s[j] == ' ')--j;
        if(j < i)return false;
        for(int k = i; k <= j; ++k)
        {
            int input = getInput(s[k]);
            state = transferTable[state][input];
            if(state == -1)return false;
        }
        return state == 2 || state == 4 || state == 7;
    }
    
private:
    int getInput(char c)
    {
        switch(c)
        {
            case '+':
            case '-':
                return 0;
            case '0':
            case '1':
            case '2':
            case '3':
            case '4':
            case '5':
            case '6':
            case '7':
            case '8':
            case '9':
                return 1;
            case '.':
                return 2;
            case 'e':
                return 3;
            default:
                return 4;
        }
    }
};