Merge pull request #753 from vaskoz/day373

Day373

README.md

@@ -368,4 +368,5 @@ problems from
 * Day 370 - Never received an e-mail for this day.
 * [Day 371](https://github.com/vaskoz/dailycodingproblem-go/issues/750)
 * [Day 372](https://github.com/vaskoz/dailycodingproblem-go/issues/748)
+* [Day 373](https://github.com/vaskoz/dailycodingproblem-go/issues/752)
 

day373/problem.go

@@ -0,0 +1,57 @@
+package day373
+
+import "sort"
+
+// LongestConsecutiveSequenceBrute runs in O(N log N)
+// due to sorting the input.
+func LongestConsecutiveSequenceBrute(nums []int) int {
+	sort.Ints(nums)
+
+	longest := 0
+	current := 1
+
+	for i := 1; i < len(nums); i++ {
+		if nums[i] == nums[i-1]+1 {
+			current++
+		} else {
+			if current > longest {
+				longest = current
+			}
+			current = 1
+		}
+	}
+
+	if current > longest {
+		longest = current
+	}
+
+	return longest
+}
+
+// LongestConsecutiveSequenceLinear runs in O(N).
+func LongestConsecutiveSequenceLinear(nums []int) int {
+	set := make(map[int]struct{}, len(nums))
+
+	for _, num := range nums {
+		set[num] = struct{}{}
+	}
+
+	longest := 0
+
+	for _, num := range nums {
+		if _, found := set[num-1]; !found {
+			found = true
+			count := 0
+
+			for ; found; count++ {
+				_, found = set[num+count+1]
+			}
+
+			if count > longest {
+				longest = count
+			}
+		}
+	}
+
+	return longest
+}

day373/problem_test.go

@@ -0,0 +1,57 @@
+package day373
+
+import "testing"
+
+// nolint
+var testcases = []struct {
+	input []int
+	lcs   int
+}{
+	{[]int{5, 2, 99, 3, 4, 1, 100}, 5},
+	{[]int{100, 4, 200, 1, 3, 2}, 4},
+	{[]int{100, 4, 101, 103, 1, 102, 3, 104, 2, 105}, 6},
+}
+
+func TestLongestConsecutiveSequenceBrute(t *testing.T) {
+	t.Parallel()
+
+	for _, tc := range testcases {
+		copied := append([]int{}, tc.input...)
+
+		if result := LongestConsecutiveSequenceBrute(copied); result != tc.lcs {
+			t.Errorf("Expected %v, got %v", tc.lcs, result)
+		}
+	}
+}
+
+func BenchmarkLongestConsecutiveSequenceBrute(b *testing.B) {
+	for i := 0; i < b.N; i++ {
+		for _, tc := range testcases {
+			copied := append([]int{}, tc.input...)
+
+			LongestConsecutiveSequenceBrute(copied)
+		}
+	}
+}
+
+func TestLongestConsecutiveSequenceLinear(t *testing.T) {
+	t.Parallel()
+
+	for _, tc := range testcases {
+		copied := append([]int{}, tc.input...)
+
+		if result := LongestConsecutiveSequenceLinear(copied); result != tc.lcs {
+			t.Errorf("Expected %v, got %v", tc.lcs, result)
+		}
+	}
+}
+
+func BenchmarkLongestConsecutiveSequenceLinear(b *testing.B) {
+	for i := 0; i < b.N; i++ {
+		for _, tc := range testcases {
+			copied := append([]int{}, tc.input...)
+
+			LongestConsecutiveSequenceLinear(copied)
+		}
+	}
+}