String to Integer (atoi)

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.

 

public class Solution {
    public int myAtoi(String str) { 
    	if (str == null || str.equals("")) {
    		return 0;
    	}
    	str = str.trim(); 
    	int i = 0;
    	boolean posi = true;
    	if (str.charAt(0) == '-') {
    		posi = false;
    		i++;
    	} else if (str.charAt(0) == '+') {
    		posi = true;
    		i++;
    	}
    	int res = 0;
    	int cur = 0;
    	for (; i < str.length() && str.charAt(i) >= '0' && str.charAt(i) <= '9'; i++) {
    		cur = str.charAt(i) - '0';
    		if(Integer.MAX_VALUE/10 < res || (Integer.MAX_VALUE/10 == res && Integer.MAX_VALUE%10 < cur)) {
    			return posi ? Integer.MAX_VALUE : Integer.MIN_VALUE;
    		}
			res = res * 10 + cur;
		}
    	return posi ? res : -res;
    }  
}