stdex/heap.d at master · Poita/stdex · GitHub

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module stdex.heap;

import std.functional;

void pushHeap(alias compare = "a < b", T)(T[] heap)
{
    pushHeap!compare(heap, heap.length - 1, 0, heap[$ - 1]);
}

void popHeap(alias compare = "a < b", T)(T[] heap)
{
    if (heap.length > 1)
        popHeap!compare(heap[0..$-1], heap[$-1]);
}

void makeHeap(alias compare = "a < b", T)(T[] heap)
{
    if (heap.length < 2)
        return;

    size_t length = heap.length;
    size_t parent = (length - 2) / 2;

    while (true)
    {
        T value = heap[parent];
        adjustHeap!compare(heap, parent, value);
        if (parent == 0)
            return;
        --parent;
    }
}

void adjustHeap(alias compare = "a < b", T)(T[] heap, size_t hole, T value)
{
    alias binaryFun!compare comp;
    const size_t top = hole;
    size_t second = hole;
    size_t length = heap.length;
    while (second < (length - 1) / 2)
    {
        second = 2 * (second + 1);
        if (comp(heap[second], heap[second - 1]))
        second--;
        heap[hole] = heap[second];
        hole = second;
    }
    if ((length & 1) == 0 && second == (length - 2) / 2)
    {
        second = 2 * (second + 1);
        heap[hole] = heap[second - 1];
        hole = second - 1;
    }
    pushHeap!compare(heap, hole, top, value);
}

private void popHeap(alias compare = "a < b", T)(T[] heap, ref T result)
{
    T value = result;
    result = heap[0];
    adjustHeap!compare(heap, 0, value);
}

private void pushHeap(alias compare = "a < b", T)(T[] heap, size_t hole, size_t top, T value)
{
    alias binaryFun!compare comp;
    size_t parent = (hole - 1) / 2;
    while (hole > top && comp(heap[parent], value))
    {
        heap[hole] = heap[parent];
        hole = parent;
        parent = (hole - 1) / 2;
    }
    heap[hole] = value;
}