String to Integer (atoi)

Implement atoi to convert a string to an integer.

 1 public class Solution {
 2     public int atoi(String str) {
 3         char[] s = str.trim().toCharArray();
 4         if(s.length==0){
 5             return 0;
 6         }
 7         long num = 0;
 8         int sign =1;
 9         int len = s.length;
10         int start = 0;
11         if(start<len&&s[start]=='+'){
12             sign=1;
13             start++;
14         }
15         if(start<len&&s[start]=='-'){
16             sign*=-1;
17             start++;
18         }
19         for(;start<len;start++){
20             if(s[start]==' ' || s[start]>'9'||s[start]<'0')
21                 break;
22             num = num*10+s[start]-'0';
23             if(num>Integer.MAX_VALUE)
24              return sign==1?Integer.MAX_VALUE:Integer.MIN_VALUE;
25         }
26         return (int)(num*sign);
27     }
28 }
View Code

long res = 0;

if(res>Integer.MAX_VALUE)return sign==1?Integer.MAX_VALUE:Integer.MIN_VALUE;

 只能用>因为负数可以到！

posted @ 2014-02-06 04:58  krunning  阅读(115)  评论(0)  编辑  收藏  举报