leetcode String to Integer (atoi)

题目

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.

这道题感觉也挺简单的，但是就是写不对，因为没有对int型最大最小考虑，实际上即使知道要考虑，也不会写。。。。

Integer.Max_value/10<result||(Integer.MAX_Value/10==result&&Integer.MAX_VALUE%10<(str.charAt(current)-'0'))

public class Solution {
    public int atoi(String str) {
        if(str==null||str.length()<1)return 0;
		str=str.trim();
		int flag=str.charAt(0)=='-'?-1:1;
		int current=0;
		if(str.charAt(0)=='+'||str.charAt(0)=='-'){
			current++;
		}
		int result=0;
		while(current<str.length()&&Character.isDigit(str.charAt(current))){
			if(Integer.MAX_VALUE/10<result||(Integer.MAX_VALUE/10==result&&
					Integer.MAX_VALUE%10<(str.charAt(current)-'0'))){
				return  flag==-1?Integer.MIN_VALUE:Integer.MAX_VALUE;
			}
			result=result*10+(str.charAt(current)-'0');
			current++;
		}
		
		if(flag==-1){
			result*=-1;
		}
		return result;
    }
}