LeetCode 8. 字符串转换整数 (atoi)

leetcode-cn.com/problems/st…

思路：把示例中的几种情况考虑到就可以了

public int myAtoi(String str) {
    if (str == null) {
        return 0;
    }
    // 忽略首尾空格
    str = str.trim();
    if (str.length() == 0) {
        return 0;
    }
    // 首字母是数字，正号，负号
    char c = str.charAt(0);
    int iVal = 0;
    int sign = 1;
    if ('-' == c) {
        sign = -1;
    } else if ('+' == c) {
    } else if (c >= '0' && c <= '9') {
        iVal = (c - '0');
    } else {
        return 0;
    }
    for (int i = 1; i < str.length(); i++) {
        char tmpC = str.charAt(i);
        if (tmpC < '0' || tmpC > '9') {
            break;
        }
        int newVal = 10 * iVal + (tmpC - '0');
        if (iVal > newVal || iVal > 214748364) {
            return sign == 1 ? Integer.MAX_VALUE : Integer.MIN_VALUE;
        }
        iVal = newVal;
    }
    return sign * iVal;
}