gno.land/r/moul/x/daily/heapdemo/v0⧉

1// Package heapdemo is a small gnoweb demo of the binary heap / priority queue2// provided by the [p/moul/x/daily/heap](/p/moul/x/daily/heap/v0) library: it3// shows min- and max-ordering and the deterministic tiebreak.4//5// It contains no heap logic of its own. Stateless, so Render is deterministic —6// which is precisely what the library is for.7package heapdemo89import (10	"strconv"11	"strings"1213	"gno.land/p/moul/x/daily/heap/v0"14)1516type job struct {17	name     string18	priority int19}2021// queue is the shared workload used by every section below.22var queue = []job{23	{"send email", 5},24	{"pay invoice", 1},25	{"backup db", 3},26	{"rotate keys", 1},27	{"clear cache", 9},28}2930// Render renders the demo for gnoweb.31func Render(path string) string {32	var b strings.Builder33	b.WriteString("# Binary Heap\n\n")34	b.WriteString("A priority queue, demoing the ")35	b.WriteString("[`p/moul/x/daily/heap`](/p/moul/x/daily/heap/v0) library.\n\n")3637	b.WriteString("## The workload\n\n")38	b.WriteString("| job | priority |\n|---|---|\n")39	for _, j := range queue {40		b.WriteString("| " + j.name + " | " + strconv.Itoa(j.priority) + " |\n")41	}4243	b.WriteString("\n## Min-heap — lowest priority first\n\n")44	b.WriteString(popOrder(fill(heap.New())))4546	b.WriteString("\n## Max-heap — highest priority first\n\n")47	b.WriteString(popOrder(fill(heap.NewMax())))4849	b.WriteString("\n## Ties\n\n")50	b.WriteString("`pay invoice` and `rotate keys` share priority 1. Both heaps pop them ")51	b.WriteString("**oldest-first**: the tiebreak is insertion order and does *not* invert ")52	b.WriteString("with the heap kind.\n\n")5354	b.WriteString("> Without a total order, two nodes could pop equal-priority items in ")55	b.WriteString("different sequences and render different pages — a consensus bug, not a ")56	b.WriteString("cosmetic one.\n")57	return b.String()58}5960func fill(h *heap.Heap) *heap.Heap {61	for _, j := range queue {62		h.Push(j.name, j.priority)63	}64	return h65}6667func popOrder(h *heap.Heap) string {68	var b strings.Builder69	b.WriteString("| # | job | priority |\n|---|---|---|\n")70	i := 071	for {72		v, p, ok := h.Pop()73		if !ok {74			break75		}76		i++77		b.WriteString("| " + strconv.Itoa(i) + " | " + v + " | " + strconv.Itoa(p) + " |\n")78	}79	return b.String()80}81