String to Integer

Implement function atoi to convert a string to an integer.

If no valid conversion could be performed, a zero value is returned.

If the correct value is out of the range of representable values, INT_MAX(2147483647) or INT_MIN (-2147483648) is returned.

Example 
"10" => 10
"-1" => -1
"123123123123123" => 2147483647
"1.0" => 1
 1 public class Solution {
 2     public int myAtoi(String str) {
 3         if (str == null || str.length() == 0)
 4             return 0;
 5         str = str.trim();
 6         if (str.length() == 1 && (str.equals("+") || str.equals("-") || str.equals(".") || str.equals("0"))) {
 7             return 0;
 8         }
 9 
10         boolean isPositive = true;
11         long current = 0;
12 
13         for (int i = 0; i < str.length(); i++) {
14             if (i == 0 && str.charAt(i) == '+') {
15                 continue;
16             } else if (i == 0 && str.charAt(i) == '-') {
17                 isPositive = false;
18             } else if (str.charAt(i) >= '0' && str.charAt(i) <= '9') {
19                 current = current * 10 + str.charAt(i) - '0';
20                 if (isPositive && current > Integer.MAX_VALUE)
21                     return Integer.MAX_VALUE;
22                 if (!isPositive && -current < Integer.MIN_VALUE)
23                     return Integer.MIN_VALUE;
24             } else {
25                 break;
26             }
27         }
28 
29         if (!isPositive) {
30             current = -current;
31         }
32 
33         return (int) current;
34     }
35 }

 

posted @ 2016-07-23 05:22  北叶青藤  阅读(215)  评论(0)  编辑  收藏  举报