Why is reading lines from stdin much slower in C++ than Python?

There are a few reasons why reading lines from standard input (stdin) may be slower in C++ than in Python:

1. C++ has to do more work to parse the input. When you read a line of input in C++, you typically have to convert the input from a string to the desired data type (e.g., integer, float, etc.). This involves additional parsing and conversion steps that are not necessary in Python, which is a dynamically-typed language and can automatically convert input to the appropriate data type.

2. C++ has to manage memory more explicitly. In C++, you have to manually allocate memory for variables and arrays, and you have to ensure that this memory is properly deallocated when you are finished with it. This can add overhead to your code, especially if you are reading large amounts of data. In Python, the memory management is handled automatically, which can make the code more efficient.

3. The Python interpreter may be optimized for reading input. The Python interpreter is implemented in C and is highly optimized for various tasks, including reading input. It may be that the Python interpreter has been optimized to read input more efficiently than the equivalent code in C++.

These are a few possible reasons why reading lines from stdin may be slower in C++ than in Python. It's worth noting that the performance difference may not be significant for small inputs, but it may become more noticeable as the input size increases.