c_cpp 8.字符串到整数atoi - Med - 2018.10.29

Posted 2021-05-14

class Solution {
public:
    int myAtoi(string str) {
        double re = 0;
        float posi = 0;
        for (auto c : str) {
            if (posi == 0
                && c == ' ') {
                continue;
            }
            // 判断正负
            if (posi == 0) {
                // 第一个字符是 "-"
                if (c == '-') {
                    posi = -1;
                    continue;
                }
                posi = 1;
                if (c == '+') {
                    continue;
                }
            }
            // 无效字符
            if (c < '0'
                || c > '9') {
                break;
            }
            re = re*10 + (c-'0');
        }
        re *= posi;
        return re >= 2147483647 ? 2147483647 : (re <= -2147483648 ? -2147483648 : re);
    }
};