#python
    def atoi(self, str):
        str = str.strip(" ")
        if len(str) == 0:
            return 0
        s = ''
        MAX_INT = 2147483647
        MIN_INT = -2147483648
        for i in range(len(str)):
            if str[i] == "+" or str[i] == "-" or str[i].isdigit():
                s += str[i]
            else:
                break
        if len(s) == 0 or (len(s) == 1 and not s[0].isdigit()):
            return 0
        if len(s) >= 2 and not s[1].isdigit():
            return 0
        s = int(s)
        if s > MAX_INT:
            return MAX_INT
        if s < MIN_INT:
            return MIN_INT
        return s

//java
public class Solution {
    public int atoi(String str) {
        String s = str.trim();
        StringBuilder sb = new StringBuilder();
        for (int i = 0; i < s.length(); i++) {
            char c = s.charAt(i);
            if (Character.isDigit(s.charAt(i)) || (i == 0 && (c == '-' || c == '+'))) {
                sb.append(c);
            }
            else break;
        }
        String rs = sb.toString();
        if (rs.length() == 0 || (rs.length() == 1 && !Character.isDigit(rs.charAt(0)))) return 0;
        if (rs.charAt(0) == '-' && rs.length() > 15) return Integer.MIN_VALUE;
        if (rs.length() > 15) return Integer.MAX_VALUE;
        if (Long.parseLong(rs) >= (long) Integer.MAX_VALUE) return Integer.MAX_VALUE;
        if (Long.parseLong(rs) <= (long) Integer.MIN_VALUE) return Integer.MIN_VALUE;
        try {
            int n = Integer.parseInt(sb.toString());
            return n;

        } catch (NumberFormatException e1) {
            return 0;
        }
    }
}