/**

* 8. 字符串转换整数 (atoi)

* https://leetcode-cn.com/problems/string-to-integer-atoi/

*

*/

class Solution {

public int myAtoi(String s) {

char[] chars = s.toCharArray();

int len = chars.length;

int index = 0;

while (index < len && chars[index] == ' '){

index++;

}

if (index == len) return 0;

int sign = 1;

char firstChar = chars[index];

if (firstChar == '-') {

index++;

sign = -1;

} else if (firstChar == '+') {

index++;

}

int res = 0, last = 0;

while (index < len) {

char c = chars[index];

if (c < '0' || c > '9') break;

int tem = c - '0';

last = res;

res = res * 10 + tem;

if (last != res / 10)

return (sign == (-1)) ? Integer.MIN_VALUE : Integer.MAX_VALUE;

index++;

}

return res * sign;

}

}