feat: longest consecutive sequence

pkg/longest_consecutive_sequence/main.go

@@ -0,0 +1,86 @@
+package longest_consecutive_sequence
+
+// type Node struct {
+// 	// The location of the parent node.
+// 	Parent *Node
+
+// 	// The number of descendent nodes, including itself.
+// 	Children int
+// }
+
+// func FindAncestor(n *Node) *Node {
+// 	ancestor := n
+
+// 	for ancestor.Parent != nil {
+// 		ancestor = ancestor.Parent
+// 	}
+
+// 	return ancestor
+// }
+
+// func LongestConsecutive(nums []int) int {
+// 	nodes := map[int]*Node{}
+
+// 	for _, num := range nums {
+// 		if _, exists := nodes[num]; exists {
+// 			continue
+// 		}
+
+// 		node := &Node{Parent: nil, Children: 1}
+
+// 		if lower, lower_exists := nodes[num-1]; lower_exists {
+// 			ancestor := FindAncestor(lower)
+// 			ancestor.Parent = node
+// 			node.Children += ancestor.Children
+// 		}
+
+// 		if upper, lower_exists := nodes[num+1]; lower_exists {
+// 			ancestor := FindAncestor(upper)
+// 			ancestor.Parent = node
+// 			node.Children += ancestor.Children
+// 		}
+
+// 		nodes[num] = node
+// 	}
+
+// 	maximum := 0
+
+// 	for _, node := range nodes {
+// 		maximum = max(maximum, node.Children)
+// 	}
+
+// 	return maximum
+// }
+
+func LongestConsecutive(nums []int) int {
+	items := map[int]bool{}
+
+	for _, num := range nums {
+		items[num] = true
+	}
+
+	maximum := 0
+
+	for item, unused := range items {
+		if !unused {
+			continue
+		}
+
+		items[item] = false
+		sequence := 1
+
+		for i := item - 1; items[i]; i-- {
+			items[i] = false
+			sequence++
+		}
+
+		for i := item + 1; items[i]; i++ {
+			items[i] = false
+			sequence++
+		}
+
+		maximum = max(maximum, sequence)
+	}
+
+	return maximum
+}

pkg/longest_consecutive_sequence/main_test.go

@@ -0,0 +1,32 @@
+package longest_consecutive_sequence_test
+
+import (
+	"testing"
+
+	"git.maximhutz.com/practice/pkg/longest_consecutive_sequence"
+	"github.com/stretchr/testify/assert"
+)
+
+func Test1(t *testing.T) {
+	assert.Equal(t, 4, longest_consecutive_sequence.LongestConsecutive([]int{100, 4, 200, 1, 3, 2}))
+}
+
+func Test2(t *testing.T) {
+	assert.Equal(t, 9, longest_consecutive_sequence.LongestConsecutive([]int{0, 3, 7, 2, 5, 8, 4, 6, 0, 1}))
+}
+
+func Test3(t *testing.T) {
+	assert.Equal(t, 3, longest_consecutive_sequence.LongestConsecutive([]int{1, 0, 1, 2}))
+}
+
+func Test4(t *testing.T) {
+	assert.Equal(t, 0, longest_consecutive_sequence.LongestConsecutive([]int{}))
+}
+
+func Test5(t *testing.T) {
+	assert.Equal(t, 7, longest_consecutive_sequence.LongestConsecutive([]int{1, 3, 5, 7, 2, 6, 4}))
+}
+
+func Test6(t *testing.T) {
+	assert.Equal(t, 7, longest_consecutive_sequence.LongestConsecutive([]int{1, 3, 5, 7, 2, 6, 4}))
+}