Java implementation of Atoi

Atoi is a function that converts a string to an integer, how does it work with Java? Looks simple, traps a lot, in the Leetcode website, this function can write completely correct probability only 14%.

atoi's need Is this:

1. If there are spaces in front, you need to exclude spaces;

2. If the first string is the + number, it is considered a positive number, if it is a negative, the

3. After the character is not a number, then return 0, if it is a number, return the actual number. The conversion ends when a character that is not a number is encountered.

public class Solution {

public int atoi (String str) {

Be careful here, you need to judge the validity.

if (Str==null | | str.length () = = 0)

{

return 0;

}

int nlen = Str.length ();

Double sum = 0;

int sign = 1;

int j = 0;

Exclude spaces

while (Str.charat (j) = = ")

j + +;

Judging positive and negative numbers

if (Str.charat (j) = = ' + ')

{

sign = 1;

j + +;

}else if (Str.charat (j) = = '-')

{

sign =-1;

j + +;

}

for (int i=j;i<nlen;i++)

{

Char current = Str.charat (i);

if (current >= ' 0 ' && <= ' 9 ')

{

sum = sum*10 + (int) (current-' 0 ');

}

Else

{

Break //hit non-digit, exit conversion

}

}

sum = sum*sign;

Be careful here, you need to judge the range.

if (Sum > Integer.max_value) {

sum = Integer.max_value;

} else if (Sum < Integer.min_value) {

sum = Integer.min_value;

}

return (int) sum;

}

}

Java implementation of Atoi