Add logic to use priority heap to implement the logic

calculator/heap.go

@@ -0,0 +1,28 @@
+package calculator
+
+type LargestNumbersHeap []int
+
+func (biggestNumbers LargestNumbersHeap) Less(first, second int) bool {
+	// pop the smallest number
+	return biggestNumbers[first] < biggestNumbers[second]
+}
+
+func (biggestNumbers LargestNumbersHeap) Len() int {
+	return len(biggestNumbers)
+}
+
+func (biggestNumbers LargestNumbersHeap) Swap(first, second int) {
+	biggestNumbers[first], biggestNumbers[second] = biggestNumbers[second], biggestNumbers[first]
+}
+
+func (biggestNumbers *LargestNumbersHeap) Push(x interface{}) {
+	*biggestNumbers = append(*biggestNumbers, x.(int))
+}
+
+func (biggestNumbers *LargestNumbersHeap) Pop() interface{} {
+	oldNumbers := *biggestNumbers
+	arrayLength := len(oldNumbers)
+	number := oldNumbers[arrayLength-1]
+	*biggestNumbers = oldNumbers[0 : arrayLength-1]
+	return number
+}

calculator/largestnumbers.go

@@ -0,0 +1,51 @@
+package calculator
+
+import (
+	"bufio"
+	"container/heap"
+	"fmt"
+	"os"
+	"strconv"
+)
+
+func calculateIncomingNumber(numbers *LargestNumbersHeap, newNumber int) *LargestNumbersHeap {
+	smallest := heap.Pop(numbers).(int)
+
+	if smallest < newNumber {
+		heap.Push(numbers, newNumber)
+	} else {
+		heap.Push(numbers, smallest)
+	}
+
+	return numbers
+}
+
+func CalculateLargestNumbers(filePath string, topX int) ([]int, error) {
+	if topX <= 0 {
+		return []int{}, nil
+	}
+
+	file, err := os.Open(filePath)
+	if err != nil {
+		return []int{}, fmt.Errorf("Could not open file %s with error %w", filePath, err)
+	}
+	scanner := bufio.NewScanner(file)
+
+	largestNumbersHeap := LargestNumbersHeap{}
+
+	for scanner.Scan() {
+		text := scanner.Text()
+		number, err := strconv.Atoi(text)
+		if err != nil {
+			return []int{}, fmt.Errorf("fail to parse text %s with error %w", text, err)
+		}
+		if len(largestNumbersHeap) < topX {
+			largestNumbersHeap = append(largestNumbersHeap, number)
+			heap.Init(&largestNumbersHeap)
+		} else {
+			calculateIncomingNumber(&largestNumbersHeap, number)
+		}
+	}
+	heap.Init(&largestNumbersHeap)
+	return largestNumbersHeap, nil
+}

calculator/largestnumbers_test.go

@@ -0,0 +1,96 @@
+package calculator
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestCalculateLargestNumbers(t *testing.T) {
+	type args struct {
+		filePath string
+		topX     int
+	}
+	tests := []struct {
+		name    string
+		args    args
+		want    []int
+		wantErr bool
+	}{
+		{
+			name: "Should return top numbers",
+			args: args{
+				filePath: "../test1.txt",
+				topX:     3,
+			},
+			want:    []int{0, 2, 5},
+			wantErr: false,
+		},
+		{
+			name: "Should throw errors",
+			args: args{
+				filePath: "../test4.txt",
+				topX:     3,
+			},
+			want:    nil,
+			wantErr: true,
+		},
+		{
+			name: "Should handle duplicate numbers well",
+			args: args{
+				filePath: "../test3.txt",
+				topX:     4,
+			},
+			want:    []int{23435, 38949, 11111, 11111},
+			wantErr: false,
+		},
+		{
+			name: "Should return all numbers when topX greater than length of array",
+			args: args{
+				filePath: "../test2.txt",
+				topX:     5,
+			},
+			want:    []int{1, 9, 3, 2},
+			wantErr: false,
+		},
+		{
+			name: "Should return 0 when topX is less then 1",
+			args: args{
+				filePath: "../test2.txt",
+				topX:     0,
+			},
+			want:    []int{},
+			wantErr: false,
+		},
+		{
+			name: "Should return 0 when topX is less then 1",
+			args: args{
+				filePath: "../test2.txt",
+				topX:     -1,
+			},
+			want:    []int{},
+			wantErr: false,
+		},
+		{
+			name: "Should throw error when fail to parse file",
+			args: args{
+				filePath: "../not_exist.txt",
+				topX:     3,
+			},
+			want:    nil,
+			wantErr: true,
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			got, err := CalculateLargestNumbers(tt.args.filePath, tt.args.topX)
+			if (err != nil) != tt.wantErr {
+				t.Errorf("CalculateLargestNumbers() error = %v, wantErr %v", err, tt.wantErr)
+				return
+			}
+			if !assert.ElementsMatch(t, got, tt.want) {
+				t.Errorf("test CalculateLargestNumbers() = %v, want %v", got, tt.want)
+			}
+		})
+	}
+}

go.mod

@@ -1,3 +1,11 @@
 module github.com/wahyd4/mryum
 
 go 1.17
+
+require github.com/stretchr/testify v1.7.0
+
+require (
+	github.com/davecgh/go-spew v1.1.0 // indirect
+	github.com/pmezard/go-difflib v1.0.0 // indirect
+	gopkg.in/yaml.v3 v3.0.0-20200313102051-9f266ea9e77c // indirect
+)

go.sum

@@ -0,0 +1,10 @@
+github.com/davecgh/go-spew v1.1.0 h1:ZDRjVQ15GmhC3fiQ8ni8+OwkZQO4DARzQgrnXU1Liz8=
+github.com/davecgh/go-spew v1.1.0/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
+github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
+github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
+github.com/stretchr/objx v0.1.0/go.mod h1:HFkY916IF+rwdDfMAkV7OtwuqBVzrE8GR6GFx+wExME=
+github.com/stretchr/testify v1.7.0 h1:nwc3DEeHmmLAfoZucVR881uASk0Mfjw8xYJ99tb5CcY=
+github.com/stretchr/testify v1.7.0/go.mod h1:6Fq8oRcR53rry900zMqJjRRixrwX3KX962/h/Wwjteg=
+gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
+gopkg.in/yaml.v3 v3.0.0-20200313102051-9f266ea9e77c h1:dUUwHk2QECo/6vqA44rthZ8ie2QXMNeKRTHCNY2nXvo=
+gopkg.in/yaml.v3 v3.0.0-20200313102051-9f266ea9e77c/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=

main.go

@@ -1,7 +1,22 @@
 package main
 
-import "fmt"
+import (
+	"fmt"
+	"os"
+
+	"github.com/wahyd4/mryum/calculator"
+)
+
+const (
+	filePath  = "./testx3.txt"
+	topNumber = 4
+)
 
 func main() {
-	fmt.Println("hello Mr. Yum")
+	topNumbers, err := calculator.CalculateLargestNumbers(filePath, topNumber)
+	if err != nil {
+		fmt.Println("Oops: " + err.Error())
+		os.Exit(1)
+	}
+	fmt.Printf("Top %d numbers are: %v", topNumber, topNumbers)
 }

test1.txt

@@ -0,0 +1,6 @@
+0
+0
+0
+2
+0
+5

test2.txt

@@ -0,0 +1,4 @@
+1
+9
+3
+2

test3.txt

@@ -0,0 +1,14 @@
+7
+1
+122
+23435
+3345
+11111
+38949
+4213
+5233
+561
+11111
+6
+1
+3

test4.txt

@@ -0,0 +1,6 @@
+1
+s
+3
+2&&^
+3
+4