LeetCode : String to Integer (atoi) [java]

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.

思路：考虑前后空格，正负号，为空等输入情况，考虑溢出，使用long类型判断当前值是否已经溢出。

public class Solution {
public int myAtoi(String str) {
if (str == null || str.equals("")) {
return 0;
}
String myStr = str.trim();
int max = Integer.MAX_VALUE;
int min = Integer.MIN_VALUE;
long result = 0;
int isPositive = 1;
int index = 0;
char begin = myStr.charAt(0);
if (begin == '-') {
isPositive = -1;
index = 1;
}
if(begin == '+'){
index = 1;
}
for (int i = index; i < myStr.length(); i++) {
char ch = myStr.charAt(i);
if (ch > '9' || ch < '0') {
return (int) result * isPositive;
} else {
result = result * 10 + ch - '0';
if (result > max || result < min) {
return isPositive == 1 ? max : min;
}
}
}
return (int) result * isPositive;
}
}