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In order to understand why this happens, you have to understand the data structures that you're working with.

Q: What is an array? A: An array is a contiguous region of memory containing a type. As far as we are concerned it can contain any type of object. But since you're working with int, in C++ an integer is tipicaly formed by 32 bits, but it depends. Therefore, your representation in memory would be something like,

| 4 bytes | 4 bytes | 4 bytes | (...) 

When you're sorting an array, the std::greater<int>operator will "sort" your array by keeping the greater integer in the first position, the second largest value in the second position, and so on.

Q: What is a std::priority_queue? A: A priority queue is a heap, more specifically, a binary tree. A heap is a data structure that is optimized to return the largest value by default. This type of heaps are called max heaps. But when you overload the comparison within the priority_queue using the std::greater operator, you are transforming the heap into a min heap. These kind of heaps, similarly to what happens when you overload the std::sort method operator, is implemented to retrieve the minimum value first.

Keep in mind that the representation of a heap in memory is completely different from the one found in an array.

In order to understand why this happens, you have to understand the data structures that you're working with.

Q: What is an array? A: An array is a contiguous region of memory containing a type. As far as we are concerned it can contain any type of object. But since you're working with int, in C++ an integer is tipicaly formed by 32 bits, but it depends. Therefore, your representation in memory would be something like,

| 4 bytes | 4 bytes | 4 bytes | (...) 

When you're sorting an array, the std::greater<int>operator will "sort" your array by keeping the greater integer in the first position, the second largest value in the second position, and so on.

Q: What is a std::priority_queue? A: A priority queue is a heap, more specifically, a binary tree. A heap is a data structure that is optimized to return the largest value by default. This type of heaps are called max heaps. But when you overload the comparison within the priority_queue using the std::greater operator, you are transforming the heap into a min heap. This kind of heaps, similarly to what happens when you overload the std::sort method operator, is implemented to retrieve the minimum value first.

Keep in mind that the representation of a heap in memory is completely different from the one found in an array.

In order to understand why this happens, you have to understand the data structures that you're working with.

Q: What is an array? A: An array is a contiguous region of memory containing a type. As far as we are concerned it can contain any type of object. But since you're working with int, in C++ an integer is tipicaly formed by 32 bits, but it depends. Therefore, your representation in memory would be something like,

| 4 bytes | 4 bytes | 4 bytes | (...) 

When you're sorting an array, the std::greater<int>operator will "sort" your array by keeping the greater integer in the first position, the second largest value in the second position, and so on.

Q: What is a std::priority_queue? A: A priority queue is a heap, more specifically, a binary tree. Which is a data structure that is optimized to return the largest value by default. This type of heaps are called max heaps. But when you overload the comparison within the priority_queue using the std::greater operator, you are transforming the heap into a min heap. These kind of heaps, similarly to what happens when you overload the std::sort method operator, is implemented to retrieve the minimum value first.

Keep in mind that the representation of a heap in memory is completely different from the one found in an array.

In order to understand why this happens, you have to understand the data structures that you're working with.

Q: What is an array? A: An array is a contiguous region of memory containing a type. As far as we are concerned it can contain any type of object. But since you're working with int, in C++ an integer is tipicaly formed by 32 bits, but it depends. Therefore, your representation in memory would be something like,

| 4 bytes | 4 bytes | 4 bytes | (...) 

When you're sorting an array, the std::greater<int>operator will "sort" your array by keeping the greater integer in the first position, the second largest value in the second position, and so on.

Q: What is a std::priority_queue? A: A priority queue is a heap, more specifically, a binary tree. A heap is a data structure that is optimized to return the largest value by default. This type of heaps are called max heaps. But when you overload the comparison within the priority_queue using the std::greater operator, you are transforming the heap into a min heap. These kind of heaps, similarly to what happens when you overload the std::sort method operator, is implemented to retrieve the minimum value first.

Keep in mind that the representation of a heap in memory is completely different from the one found in an array.

In order to understand why this happens, you have to understand the data structures that you're working with.

Q: What is an array? A: An array is a contiguous region of memory containing a type. As far as we are concerned it can contain any type of object. But since you're working with int, in C++ an integer is formed by 32 bits on 64 bits machines, but it depends. Therefore, your representation in memory would be something like,

| 4 bytes | 4 bytes | 4 bytes | (...) 

When you're sorting an array, the std::greater<int>operator will "sort" your array by keeping the greater integer in the first position, the second largest value in the second position, and so on.

Q: What is a std::priority_queue? A: A priority queue is a heap, more specifically, a binary tree. Which is a data structure that is optimized to return the larger value by default. This type of heaps are called max heaps. But when you overload the comparison within the priority_queue using the std::greater operator, you are transforming the heap into a min heap. These kind of heaps, similarly to what happens when you overload the std::sort method operator, is implemented to retrieve the minimum value first.

Keep in mind that the representation of a heap in memory is completely different from the one found in an array.

In order to understand why this happens, you have to understand the data structures that you're working with.

Q: What is an array? A: An array is a contiguous region of memory containing a type. As far as we are concerned it can contain any type of object. But since you're working with int, in C++ an integer is tipicaly formed by 32 bits, but it depends. Therefore, your representation in memory would be something like,

| 4 bytes | 4 bytes | 4 bytes | (...) 

When you're sorting an array, the std::greater<int>operator will "sort" your array by keeping the greater integer in the first position, the second largest value in the second position, and so on.

Q: What is a std::priority_queue? A: A priority queue is a heap, more specifically, a binary tree. Which is a data structure that is optimized to return the largest value by default. This type of heaps are called max heaps. But when you overload the comparison within the priority_queue using the std::greater operator, you are transforming the heap into a min heap. These kind of heaps, similarly to what happens when you overload the std::sort method operator, is implemented to retrieve the minimum value first.

Keep in mind that the representation of a heap in memory is completely different from the one found in an array.