Implement atoi to convert a string to an integer.
Hint: Carefully consider all possible input cases. If you want a challenge, please do not see below and ask yourself what are the possible input cases.
Notes: It is intended for this problem to be specified vaguely (ie, no given input specs). You are responsible to gather all the input requirements up front.
题目含义：实现atoi功能
1 public int myAtoi(String str) { 2 if (str == null || str.length() == 0) 3 return 0;// 4 str = str.trim(); 5 char firstChar = str.charAt(0); 6 int sign = 1, start = 0, len = str.length(); 7 long sum = 0; 8 if (firstChar == '+') { 9 sign = 1; 10 start++; 11 } else if (firstChar == '-') { 12 sign = -1; 13 start++; 14 } 15 for (int i = start; i < len; i++) { 16 if (!Character.isDigit(str.charAt(i))) 17 return (int) sum * sign; 18 sum = sum * 10 + str.charAt(i) - '0'; 19 if (sign == 1 && sum > Integer.MAX_VALUE) 20 return Integer.MAX_VALUE; 21 if (sign == -1 && (-1) * sum < Integer.MIN_VALUE) 22 return Integer.MIN_VALUE; 23 } 24 25 return (int) sum * sign; 26 }