12345678910111213141516171819202122232425262728293031323334353637383940414243444546474849505152535455565758 |
- class Solution {
- // Numbers 0-9
- // Exponent - "e"
- // Positive/negative sign - "+"/"-"
- // Decimal point - "."
- public boolean isNumber(String s) {
- // Finite automaton
- // State No. | Discription
- // -1 | Invalid state
- // 0 | Initail state
- // 1 | Input sign
- // 2 | Input digit
- // 3 | Input dot
- // 4 | Input digit and dot
- // 5 | Input exp
- // 6 | Input sign after exp
- // 7 | Input digit after exp
- // 8 | Input space after valid number
- // Input state:
- // INVALID, SPACE, SIGN, DIGIT, DOT, EXP
- // Trans table:
- // input ERR SPA SGN DIG DOT EXP
- // state
- // 0 -1 0 1 2 3 -1
- // 1 -1 -1 -1 2 3 -1
- // 2 -1 8 -1 2 3 5
- // 3 -1 -1 -1 4 -1 5
- // 4 -1 8 -1 4 -1 5
- // 5 -1 -1 6 7 -1 -1
- // 6 -1 -1 -1 7 -1 -1
- // 7 -1 8 -1 7 -1 -1
- // 8 -1 8 -1 -1 -1 -1
- char[] num = s.toCharArray();
- int[][] stateTable = new int[][] {
- {-1, 0, 1, 2, 3, -1}, // 0
- {-1, -1, -1, 2, 3, -1}, // 1
- {-1, 8, -1, 2, 4, 5}, // 2
- {-1, -1, -1, 4, -1, -1}, // 3
- {-1, 8, -1, 4, -1, 5}, // 4
- {-1, -1, 6, 7, -1, -1}, // 5
- {-1, -1, -1, 7, -1, -1}, // 6
- {-1, 8, -1, 7, -1, -1}, // 7
- {-1, 8, -1, -1, -1, -1} // 8
- };
- int state = 0;
- for (int i = 0; i < num.length; i++) {
- int input = 0;
- if (num[i] == ' ') input = 1;
- else if (num[i] == '+' || num[i] == '-') input = 2;
- else if ('0' <= num[i] && num[i] <= '9') input = 3;
- else if (num[i] == '.') input = 4;
- else if (num[i] == 'e' || num[i] == 'E') input = 5;
- state = stateTable[state][input];
- if (state == -1) return false;
- }
- return state == 2 || state == 4 || state == 7 || state == 8;
- }
- }
|