- P008 String to Integer atoi
- 思路分析
- 代码
- java
- python
P008 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.
思路分析
关键是注意特殊情况的处理:
- 输入空字符==>0
- 对输入进行trim
- 注意可能出现的正号(+)和负号(-)
- 读取到非字符时停止,并将前面的结果返回
- 注意溢出问题==>
Integer.MAX_VALUE 或者 Integer.MIN_VALUE
代码
java
public class Solution008 {
public int myAtoi(String str) {
if (str == null)
return ;
str = str.trim();
if ("".equals(str))
return ;
StringBuilder sb = new StringBuilder();
int sign = ;
if (str.startsWith("+")) {
str = str.replaceFirst("\\+", "");
} else if (str.startsWith("-")) {
sign = -;
str = str.replaceFirst("-", "");
}
for (int i = ; i < str.length(); i++) {
char c = str.charAt(i);
if (c > '9' || c < '0') {
break;
}
sb.append(c);
}
try {
long l = sign * Long.parseLong(sb.toString());
if (l >= Integer.MAX_VALUE)
return Integer.MAX_VALUE;
if (l <= Integer.MIN_VALUE)
return Integer.MIN_VALUE;
return (int) (l);
} catch (Exception e) {
// e.printStackTrace();
return ;
}
}
public static void main(String[] args) {
System.out.println(Integer.MIN_VALUE);
System.out.println(Integer.MAX_VALUE);
Solution008 s8 = new Solution008();
String strs[] = { //
"", "-2147483648", "-2147483649", "2147483648", "-2147483648", //
"1010023630", "-1010023630", //
" 10522545459", " 10522545459+123 ", //
"-123", "+123", " -123 ", "+123sdf", //
"11111111111111111111111111111111111111111111111111", //
"sfjdk", "-fjdks", "+fjsdk" };
for (String s : strs) {
System.out.println(s + "-->" + s8.myAtoi(s));
}
}
}
python
class Solution008(object):
def myAtoi(self, s):
"""
:type str: str
:rtype: int
"""
if not s:return
s = s.strip()
if "" == s:return
sign = ;strs = "0"
if s[] == "+":
s = s[:]
elif s[] == "-":
sign = -
s = s[:]
for c in s:
if c > '9' or c < '0':
break
strs += c
l = long(strs) * sign
if l <= -:return -
if l >= :return
return (int)(l)