github.com/mailgun/holster/v4@v4.20.0/collections/priority_queue_test.go (about)

     1  /*
     2  Copyright 2017 Mailgun Technologies Inc
     3  
     4  Licensed under the Apache License, Version 2.0 (the "License");
     5  you may not use this file except in compliance with the License.
     6  You may obtain a copy of the License at
     7  
     8  	http://www.apache.org/licenses/LICENSE-2.0
     9  
    10  Unless required by applicable law or agreed to in writing, software
    11  distributed under the License is distributed on an "AS IS" BASIS,
    12  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    13  See the License for the specific language governing permissions and
    14  limitations under the License.
    15  */
    16  package collections_test
    17  
    18  import (
    19  	"fmt"
    20  	"testing"
    21  
    22  	"github.com/mailgun/holster/v4/collections"
    23  	"github.com/stretchr/testify/assert"
    24  )
    25  
    26  func toPtr(i int) interface{} {
    27  	return &i
    28  }
    29  
    30  func toInt(i interface{}) int {
    31  	return *(i.(*int))
    32  }
    33  
    34  func TestPeek(t *testing.T) {
    35  	mh := collections.NewPriorityQueue()
    36  
    37  	el := &collections.PQItem{
    38  		Value:    toPtr(1),
    39  		Priority: 5,
    40  	}
    41  
    42  	mh.Push(el)
    43  	assert.Equal(t, 1, toInt(mh.Peek().Value))
    44  	assert.Equal(t, 1, mh.Len())
    45  
    46  	el = &collections.PQItem{
    47  		Value:    toPtr(2),
    48  		Priority: 1,
    49  	}
    50  	mh.Push(el)
    51  	assert.Equal(t, 2, mh.Len())
    52  	assert.Equal(t, 2, toInt(mh.Peek().Value))
    53  	assert.Equal(t, 2, toInt(mh.Peek().Value))
    54  	assert.Equal(t, 2, mh.Len())
    55  
    56  	el = mh.Pop()
    57  
    58  	assert.Equal(t, 2, toInt(el.Value))
    59  	assert.Equal(t, 1, mh.Len())
    60  	assert.Equal(t, 1, toInt(mh.Peek().Value))
    61  
    62  	mh.Pop()
    63  	assert.Equal(t, 0, mh.Len())
    64  }
    65  
    66  func TestUpdate(t *testing.T) {
    67  	mh := collections.NewPriorityQueue()
    68  	x := &collections.PQItem{
    69  		Value:    toPtr(1),
    70  		Priority: 4,
    71  	}
    72  	y := &collections.PQItem{
    73  		Value:    toPtr(2),
    74  		Priority: 3,
    75  	}
    76  	z := &collections.PQItem{
    77  		Value:    toPtr(3),
    78  		Priority: 8,
    79  	}
    80  	mh.Push(x)
    81  	mh.Push(y)
    82  	mh.Push(z)
    83  	assert.Equal(t, 2, toInt(mh.Peek().Value))
    84  
    85  	mh.Update(z, 1)
    86  	assert.Equal(t, 3, toInt(mh.Peek().Value))
    87  
    88  	mh.Update(x, 0)
    89  	assert.Equal(t, 1, toInt(mh.Peek().Value))
    90  }
    91  
    92  func ExampleNewPriorityQueue() {
    93  	queue := collections.NewPriorityQueue()
    94  
    95  	queue.Push(&collections.PQItem{
    96  		Value:    "thing3",
    97  		Priority: 3,
    98  	})
    99  
   100  	queue.Push(&collections.PQItem{
   101  		Value:    "thing1",
   102  		Priority: 1,
   103  	})
   104  
   105  	queue.Push(&collections.PQItem{
   106  		Value:    "thing2",
   107  		Priority: 2,
   108  	})
   109  
   110  	// Pops item off the queue according to the priority instead of the Push() order
   111  	item := queue.Pop()
   112  
   113  	fmt.Printf("Item: %s", item.Value.(string))
   114  
   115  	// Output: Item: thing1
   116  }