String/Integer

8. String to Integer (atoi)

My Solutions:

public class Solution {
    public int myAtoi(String str) {
        if (str == null || str.length() == 0) return 0;
        str = str.trim();
        
	int i = 0, ans = 0, sign = 1;
	
	if (str.charAt(i) == '+' || str.charAt(i) == '-')
	    sign = (str.charAt(i++) == '+' ? 1 : -1);
	
	for (; i < str.length(); i++) {
	    int tmp = str.charAt(i) - '0';
	    if (tmp < 0 || tmp > 9）break;
		
            // 防止溢出		
	    if (ans > Integer.MAX_VALUE / 10 || (ans == Integer.MAX_VALUE / 10 && Integer.MAX_VALUE % 10 < tmp))
		return sign == 1 ? Integer.MAX_VALUE : Integer.MIN_VALUE;
	    else
		ans = ans * 10 + tmp;
	}
	return sign * ans;
    }
}