Java 代码

class Solution {
    public int strToInt(String str) {

        long num = 0;
        boolean neg = false;

        //trim
        String str1 = str.trim();

        for (int i = 0; i < str1.length(); i ++)
        {
            if (str1.charAt(i) == '-' )
            {
                neg = true;
                continue;
            }

            if (str1.charAt(i) == '+' )
                continue;

            if (!Character.isDigit(str1.charAt(i)))
                break;

            num = num * 10 + (long)(str1.charAt(i) - '0');
        }

        if (neg)
            num *= -1;

        if (num > Integer.MAX_VALUE)
            return Integer.MAX_VALUE;

        if (num < Integer.MIN_VALUE)
            return Integer.MIN_VALUE;

        return (int)num;
    }
}