class Solution {
    public int myAtoi(String str) {
    str = str.trim();
    if (str.isEmpty())
    	return 0;
    int sign = 1; int i = 0;
    if (str.charAt(0) == '-' || str.charAt(0) == '+'){
    	sign = (str.charAt(0) == '-')? -1 : 1;
    	if (str.length() < 2 || !Character.isDigit(str.charAt(1))) {
    		return 0;
    	}
    	i++;
     }
    int n = 0;
    while (i < str.length()) {
    	if (Character.isDigit(str.charAt(i))) {
    		int d = str.charAt(i) - '0';
    		if (n > (Integer.MAX_VALUE - d) / 10) { //Detect the integer overflow.
    			n = (sign == -1)? Integer.MIN_VALUE : Integer.MAX_VALUE;
    			return n;
    		}
    		n = n*10 + d;
    	} else {
    		break;
    	}
    	i++;
    }
    return sign * n;
    }
}