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@@ -6,30 +6,32 @@ class Solution {
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public boolean isNumber(String s) {
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// Finite automaton
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// State No. | Discription
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+ // ----------+------------
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// -1 | Invalid state
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- // 0 | Initail state
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+ // 0 | Initial state
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// 1 | Input sign
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// 2 | Input digit
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// 3 | Input dot
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- // 4 | Input digit and dot
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+ // 4 | Input digit and dot (like .33 or 33. or 3.3)
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// 5 | Input exp
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// 6 | Input sign after exp
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// 7 | Input digit after exp
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// 8 | Input space after valid number
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// Input state:
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- // INVALID, SPACE, SIGN, DIGIT, DOT, EXP
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+ // ERROR, SPACE, SIGN, DIGIT, DOT, EXP
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// Trans table:
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- // input ERR SPA SGN DIG DOT EXP
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- // state
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- // 0 -1 0 1 2 3 -1
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- // 1 -1 -1 -1 2 3 -1
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- // 2 -1 8 -1 2 3 5
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- // 3 -1 -1 -1 4 -1 5
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- // 4 -1 8 -1 4 -1 5
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- // 5 -1 -1 6 7 -1 -1
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- // 6 -1 -1 -1 7 -1 -1
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- // 7 -1 8 -1 7 -1 -1
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- // 8 -1 8 -1 -1 -1 -1
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+ // \input| ERR SPA SGN DIG DOT EXP
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+ // state\ |
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+ // -----------+------------------------
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+ // 0 | -1 0 1 2 3 -1
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+ // 1 | -1 -1 -1 2 3 -1
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+ // 2 | -1 8 -1 2 3 5
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+ // 3 | -1 -1 -1 4 -1 5
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+ // 4 | -1 8 -1 4 -1 5
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+ // 5 | -1 -1 6 7 -1 -1
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+ // 6 | -1 -1 -1 7 -1 -1
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+ // 7 | -1 8 -1 7 -1 -1
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+ // 8 | -1 8 -1 -1 -1 -1
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char[] num = s.toCharArray();
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int[][] stateTable = new int[][] {
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{-1, 0, 1, 2, 3, -1}, // 0
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@@ -44,12 +46,12 @@ class Solution {
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};
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int state = 0;
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for (int i = 0; i < num.length; i++) {
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- int input = 0;
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- if (num[i] == ' ') input = 1;
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- else if (num[i] == '+' || num[i] == '-') input = 2;
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- else if ('0' <= num[i] && num[i] <= '9') input = 3;
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- else if (num[i] == '.') input = 4;
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- else if (num[i] == 'e' || num[i] == 'E') input = 5;
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+ int input = 0; // ERROR
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+ if (num[i] == ' ') input = 1; // SPACE
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+ else if (num[i] == '+' || num[i] == '-') input = 2; // SIGN
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+ else if ('0' <= num[i] && num[i] <= '9') input = 3; // DIGIT
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+ else if (num[i] == '.') input = 4; // DOT
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+ else if (num[i] == 'e' || num[i] == 'E') input = 5; // EXP
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state = stateTable[state][input];
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if (state == -1) return false;
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}
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