Java | Leetcode Java题解之第8题字符串转换整数atoi

题目：

题解：

class Solution {public int myAtoi(String str) {Automaton automaton = new Automaton();int length = str.length();for (int i = 0; i < length; ++i) {automaton.get(str.charAt(i));}return (int) (automaton.sign * automaton.ans);}
}class Automaton {public int sign = 1;public long ans = 0;private String state = "start";private Map<String, String[]> table = new HashMap<String, String[]>() {{put("start", new String[]{"start", "signed", "in_number", "end"});put("signed", new String[]{"end", "end", "in_number", "end"});put("in_number", new String[]{"end", "end", "in_number", "end"});put("end", new String[]{"end", "end", "end", "end"});}};public void get(char c) {state = table.get(state)[get_col(c)];if ("in_number".equals(state)) {ans = ans * 10 + c - '0';ans = sign == 1 ? Math.min(ans, (long) Integer.MAX_VALUE) : Math.min(ans, -(long) Integer.MIN_VALUE);} else if ("signed".equals(state)) {sign = c == '+' ? 1 : -1;}}private int get_col(char c) {if (c == ' ') {return 0;}if (c == '+' || c == '-') {return 1;}if (Character.isDigit(c)) {return 2;}return 3;}
}