模拟题，感觉挺复杂的

class Solution {
public:
    int myAtoi(string str) {
        int len = str.size();
        int i = 0, flag = 1;
        long long base = 0;

        // 跳过前导空格
        while (i < len && str[i] == ' ') {
            i++;
        }

        if (i < len && (str[i] == '-' || str[i] == '+')) {
            flag = (str[i] == '-') ? -1 : 1;
            i++;
        }

        while (i < len && str[i] >= '0' && str[i] <= '9') {
            base = base * 10 + (str[i] - '0');
            i++;
            
            // 检查溢出
            if (base * flag > INT_MAX) return INT_MAX;
            if (base * flag < INT_MIN) return INT_MIN;
        }

        return flag * base;
    }
};