import java.util.HashMap;
import java.util.Map;

/**
 * 剑指offer20. 表示数值的字符串
 */

public class IsNumber {
    public boolean isNumber(String s) {
        Map[] states = {
                new HashMap<Character, Integer>() {{ put(' ', 0); put('s', 1); put('d', 2); put('.', 4);}},               // 0.
                new HashMap<Character, Integer>() {{ put('d', 2); put('.', 4);}},                            // 1.
                new HashMap<Character, Integer>() {{ put('d', 2); put('.', 3); put('e', 5); put(' ', 8);}},  // 2.
                new HashMap<Character, Integer>() {{ put('d', 3); put('e', 5); put(' ', 8); }},              // 3.
                new HashMap<Character, Integer>() {{ put('d', 3); }},                                        // 4.
                new HashMap<Character, Integer>() {{ put('s', 6); put('d', 7); }},                           // 5.
                new HashMap<Character, Integer>() {{ put('d', 7); }},                                        // 6.
                new HashMap<Character, Integer>() {{ put('d', 7); put(' ', 8); }},                           // 7.
                new HashMap<Character, Integer>() {{ put(' ', 8); }}
        };
        int p = 0;
        char t;
        for(char c : s.toCharArray()) {
            if(c >= '0' && c <= '9') t = 'd';
            else if(c == '+' || c == '-') t = 's';
            else if(c == 'e' || c == 'E') t = 'e';
            else if(c == '.' || c == ' ') t = c;
            else t = '?';
            if(!states[p].containsKey(t)) return false;
            p = (int)states[p].get(t);
        }
        return p == 2 || p == 3 || p == 7 || p == 8;

    }
}