From a6bdd397763e1b28038926b631ff68b18891f1b1 Mon Sep 17 00:00:00 2001 From: Chewing_Bever Date: Thu, 26 Jan 2023 11:03:41 +0100 Subject: [PATCH] docs(heap): add readme --- src/heap/README.md | 33 +++++++++++++++++++++++++++++++++ 1 file changed, 33 insertions(+) create mode 100644 src/heap/README.md diff --git a/src/heap/README.md b/src/heap/README.md new file mode 100644 index 0000000..8942763 --- /dev/null +++ b/src/heap/README.md @@ -0,0 +1,33 @@ +This min-heap implementation is a pretty standard binomial heap. + +## Representation in memory + +A heap consists of one or more binomial trees, each with a different order `k` +and `2^k` total nodes. This heap can contain `2^64 - 1` elements at most, which +is far more than your memory can contain, but it's still fun to mention. + +A tree does not have its own memory structure; a node that's the root of a +binomial tree is simply called the tree. + +Each node has the following layout: + +```c +typedef struct vieter_heap_node { + uint64_t key; + void *data; + struct vieter_heap_node *largest_order; + union { + struct vieter_heap_node *next_tree; + struct vieter_heap_node *next_largest_order; + } ptr; + uint8_t order; +} vieter_heap_node; +``` + +Each node has a pointer to its child with the largest order (if the node's +order is `0`, this pointer will be NULL). Each non-root node has a pointer to +its sibling with the next-highest order. These pointers allow the children of a +binomial tree to be recombined into a new tree, once their root has been +pop'ed. + +Roots point to the binomial tree in the heap with the next largest order.