day 191: minimum intervals to remove to avoid overlaps

day191/problem.go

@@ -0,0 +1,26 @@
+package day191
+
+import "sort"
+
+// Interval has a start and end.
+type Interval struct {
+	Start, End int
+}
+
+// MinRemoveNoOverlap returns the minimum number of intervals
+// to remove to remove all overlaps.
+// Runs in O(N log N) time.
+func MinRemoveNoOverlap(intervals []Interval) int {
+	sort.Slice(intervals, func(i, j int) bool {
+		return intervals[i].End < intervals[j].End
+	})
+	count := 0
+	current := -int(^uint(0)>>1) - 1
+	for _, interval := range intervals {
+		if interval.Start >= current {
+			count++
+			current = interval.End
+		}
+	}
+	return len(intervals) - count
+}

day191/problem_test.go

@@ -0,0 +1,27 @@
+package day191
+
+import "testing"
+
+var testcases = []struct {
+	intervals []Interval
+	removes   int
+}{
+	{[]Interval{{7, 9}, {2, 4}, {5, 8}}, 1},
+}
+
+func TestMinRemoveNoOverlap(t *testing.T) {
+	t.Parallel()
+	for _, tc := range testcases {
+		if result := MinRemoveNoOverlap(tc.intervals); result != tc.removes {
+			t.Errorf("Expected %v, got %v", tc.removes, result)
+		}
+	}
+}
+
+func BenchmarkMinRemoveNoOverlap(b *testing.B) {
+	for i := 0; i < b.N; i++ {
+		for _, tc := range testcases {
+			MinRemoveNoOverlap(tc.intervals)
+		}
+	}
+}