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;

}

}