C++ 将两个字符串交叉链接

怎么将两个字符串交叉链接啊
str1＝"abcd"
str2="ABCD"
使str3=aAbBcCdD
尽量不用指针 求解答谢谢

int main()
{
    char str1[] = "abcd";
    char str2[] = "ABCDFGHI";
    char str3[20];
    int i = 0, l = 0;

    while(str1[i] && str2[i])
    {
        str3[l++] = str1[i];
        str3[l++] = str2[i];
        i++;
    }

    while(str1[i])
    {
        str3[l++] = str1[i++];
    }

    while(str2[i])
    {
        str3[l++] = str2[i++];
    }

    str3[l++] = '\0';
    cout << str3 << endl;

    system("pause");
    return 0;
}