LeetCode -- 8. String to Integer

陆陆续续在LeetCode上刷了一些题，一直没有记录过，准备集中整理记录一下

class Solution {
    public int myAtoi(String str) {
         str = str.trim();
         if (str == null || str.length() < 1) {
             return 0;
         }
         int i = 0;
         char flag = '+';
         if (str.charAt(0) == '-') {
             flag = '-';
             i++;
         } else if (str.charAt(0) == '+') {
             i++;
         }
         double res = 0;
         while (i < str.length() && str.charAt(i) >= '0' && str.charAt(i) <= '9') {
             res = res * 10 + str.charAt(i) - '0';
             i++;
         }
         if (flag == '-') res = -1 * res;
            if (res > Integer.MAX_VALUE) {
                return Integer.MAX_VALUE;
            } else if (res < Integer.MIN_VALUE) {
                return Integer.MIN_VALUE;
            }
            return (int) res;
    }
}