day 257: smallest window to sort entire

day257/problem.go

@@ -0,0 +1,26 @@
+package day257
+
+// SmallestWindowThatMustBeSorted returns the smallest window that must be
+// sorted to result in a completely sorted slice.
+func SmallestWindowThatMustBeSorted(nums []int) (start, end int) {
+	maxSoFar := -int(^uint(0)>>1) - 1
+	for i := range nums {
+		if maxSoFar < nums[i] {
+			maxSoFar = nums[i]
+		}
+		if nums[i] < maxSoFar {
+			end = i
+		}
+	}
+	minSoFar := int(^uint(0) >> 1)
+	for i := range nums {
+		j := len(nums) - 1 - i
+		if minSoFar > nums[j] {
+			minSoFar = nums[j]
+		}
+		if nums[j] > minSoFar {
+			start = j
+		}
+	}
+	return
+}

day257/problem_test.go

@@ -0,0 +1,28 @@
+package day257
+
+import "testing"
+
+// nolint
+var testcases = []struct {
+	nums       []int
+	start, end int
+}{
+	{[]int{3, 7, 5, 6, 9}, 1, 3},
+}
+
+func TestSmallestWindowThatMustBeSorted(t *testing.T) {
+	t.Parallel()
+	for _, tc := range testcases {
+		if start, end := SmallestWindowThatMustBeSorted(tc.nums); start != tc.start || end != tc.end {
+			t.Errorf("Expected (%v,%v), got (%v,%v)", tc.start, tc.end, start, end)
+		}
+	}
+}
+
+func BenchmarkSmallestWindowThatMustBeSorted(b *testing.B) {
+	for i := 0; i < b.N; i++ {
+		for _, tc := range testcases {
+			SmallestWindowThatMustBeSorted(tc.nums)
+		}
+	}
+}