github.com/shogo82148/std@v1.22.1-0.20240327122250-4e474527810c/container/heap/example_pq_test.go (about)

     1  // Copyright 2012 The Go Authors. All rights reserved.
     2  // Use of this source code is governed by a BSD-style
     3  // license that can be found in the LICENSE file.
     4  
     5  // This example demonstrates a priority queue built using the heap interface.
     6  package heap_test
     7  
     8  import (
     9  	"github.com/shogo82148/std/container/heap"
    10  	"github.com/shogo82148/std/fmt"
    11  )
    12  
    13  // This example creates a PriorityQueue with some items, adds and manipulates an item,
    14  // and then removes the items in priority order.
    15  func Example_priorityQueue() {
    16  	// Some items and their priorities.
    17  	items := map[string]int{
    18  		"banana": 3, "apple": 2, "pear": 4,
    19  	}
    20  
    21  	// Create a priority queue, put the items in it, and
    22  	// establish the priority queue (heap) invariants.
    23  	pq := make(PriorityQueue, len(items))
    24  	i := 0
    25  	for value, priority := range items {
    26  		pq[i] = &Item{
    27  			value:    value,
    28  			priority: priority,
    29  			index:    i,
    30  		}
    31  		i++
    32  	}
    33  	heap.Init(&pq)
    34  
    35  	// Insert a new item and then modify its priority.
    36  	item := &Item{
    37  		value:    "orange",
    38  		priority: 1,
    39  	}
    40  	heap.Push(&pq, item)
    41  	pq.update(item, item.value, 5)
    42  
    43  	// Take the items out; they arrive in decreasing priority order.
    44  	for pq.Len() > 0 {
    45  		item := heap.Pop(&pq).(*Item)
    46  		fmt.Printf("%.2d:%s ", item.priority, item.value)
    47  	}
    48  	// Output:
    49  	// 05:orange 04:pear 03:banana 02:apple
    50  }