class Solution {
    public int strToInt(String str) {
        if(str == null || str.length() == 0){
            return 0;
        }
        int i = 0;
        char[] chs = str.toCharArray();
        int n = chs.length;
        // 处理空格
        while(i < n && chs[i] == ' '){
            i++;
        }
        int sign = 1;
        // 处理正负号
        if(chs[i] == '-'){
            sign = -1;
            i++;
        }else if(chs[i] == '+'){
            sign = 1;
            i++;
        }
        int num = 0;
        // 处理数字部分
        while(i < n && Character.isDigit(chs[i])){
            int b = sign*(chs[i++]-'0');
            if(num > Integer.MAX_VALUE/10 || num == Integer.MAX_VALUE/10 && b > 7){
                return Integer.MAX_VALUE;
            }
            if(num < Integer.MIN_VALUE/10 || num == Integer.MIN_VALUE/10 && b < -8){
                return Integer.MIN_VALUE;
            }
            num = num*10 + b;
        }
        return num;
    }
}