String to Integer (atoi)

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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.

java

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public class Solution {
public static int myAtoi(String str) {
	        if(str==null||str.length()<1)
	        {
	            return 0;
	        }
	        //去两边的空白
	        str=str.trim();
	        //判断正负
	        int flag=1;
	        int i=0;
	        if(str.charAt(0)=='+')
	        {
	            i++;
	        }
	        if(str.charAt(0)=='-')
	        {
	            flag=-1;
	            i++;
	        }
	        //保存在double类型下，防止溢出
	        double result=0;
	        for(;i<str.length();i++)
	        {
	            if(str.charAt(i)>='0'&&str.charAt(i)<='9')
	            {
	                result=result*10+(str.charAt(i)-'0');
	            }
	            else
	                break;
	        }
	        if(flag==-1)
	            result*=-1;
	        //处理边界情况
	        if(result>Integer.MAX_VALUE)
	            result=Integer.MAX_VALUE;
	        if(result<Integer.MIN_VALUE)
	            result=Integer.MIN_VALUE;
	        return (int)result;
	        
	    }
}