字符串初始化时的注意点

1. 如果不是以'\0'结尾的char数组,去初始化string时一定要带上长度;而以'\0'结尾的char数组,则不需要.
    char no_null[] = {'H', 'i'};
    string str(no_null);    //runtime error:not null-terminated. str: Hi烫烫烫hX?
    string str2(no_null, 2);

    char c_array[] = "Hi";
    string str3(c_array);    //this is right;