String to Integer

题目：

Given a string, convert it to an integer. You may assume the string is a valid integer number that can be presented by a signed 32bit integer (-231 ~ 231-1).

分析：

不管怎么说还是比atoi II好做不少

解法

public class Solution {
    /**
     * @param str a string
     * @return an integer
     */
    public int stringToInteger(String str) {
        // Write your code here
        if (str.length() == 0) {
            return 0;
        }
        boolean flag = true;
        int start = 0;
        if (str.charAt(0) == '-') {
            flag = false;
            start++;
        }

        int res = 0;
        for (int i = start; i < str.length(); i++) {
            int temp = str.charAt(i) - '0';
            res = res * 10 + temp;
        }

        if (flag == false) {
            res = -res;
        }
        return res;
    }
}