temp = arr[i]; arr[i] = arr[max_index]; arr[max_index] = temp;

This code snippet is likely part of a sorting algorithm that swaps the values of two elements in an array.

`temp = arr[i];` assigns the value at the `i`th index of the array `arr` to a temporary variable `temp`.

`arr[i] = arr[max_index];` assigns the value at the `max_index`th index of the array `arr` to the `i`th index of the array `arr`.

`arr[max_index] = temp;` assigns the value of `temp` (which was the original value at the `i`th index of `arr`) to the `max_index`th index of `arr`.

Overall, this code snippet effectively swaps the values of the elements at indices `i` and `max_index` in `arr`.