8. String to Integer (atoi)

Medium
Zillow OA其实做过:
这道题edge case跟屎一样多,各种千奇百怪的input.

关键点在于:
if (res > Integer.MAX_VALUE / 10){if (res == Integer.MAX_VALUE / 10){这里。

class Solution {
    public int myAtoi(String str) {
        if (str == null || str.length() == 0){
            return 0;
        } 
        str = str.trim();
        if (str.length() == 0){
            return 0;
        }
        int res = 0;
        int start = 0;
        boolean isNegative = false;
        if (str.charAt(start) == '-'){
            isNegative = true;
            start++;
        } else if (str.charAt(start) == '+'){
            start++;
        }
        for (int i = start; i < str.length(); i++){
            char c = str.charAt(i);
            if (c == '+' || c == '-'){
                return 0;
            }
            if (! (c >='0' && c <= '9')){
                break;
            }
            //"-11919730356x"
            //-1191973035
            if (res > Integer.MAX_VALUE / 10){
                if (isNegative){
                    return Integer.MIN_VALUE;
                } else {
                    return Integer.MAX_VALUE;
                }
            }
            if (res == Integer.MAX_VALUE / 10){
                if (isNegative && c > '8'){
                    return Integer.MIN_VALUE;
                } else if (!isNegative && c > '7'){
                    return Integer.MAX_VALUE;
                }
            }
            res = res*10 + c - '0'; 
            System.out.println(res);
        }
        if (isNegative){
            return - res;
        } else {
            return res;
        }
    }
}

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