First successful submission of hard task No 239

239-sliding-window-maximum.go

@@ -0,0 +1,91 @@
+package main
+
+type Window struct {
+	nums      []int
+	begin     int
+	end       int
+	size      int
+	numsCount int
+}
+
+func (w *Window) Next() *Window {
+	if w.end+1 >= w.numsCount {
+		return nil
+	}
+	w.begin++
+	w.end++
+	return w
+}
+
+func (w *Window) InWindow(index int) bool {
+	return (index >= w.begin) && (index <= w.end)
+}
+
+func maxBruteForce(nums []int, begin int, end int) WindowMaximum {
+	max := nums[begin]
+	index := begin
+	for i := begin + 1; i <= end; i++ {
+		if nums[i] > max {
+			max = nums[i]
+			index = i
+		}
+	}
+
+	return WindowMaximum{index: index, value: max, valid: true}
+}
+
+func (w *Window) Max(prevMax WindowMaximum) WindowMaximum {
+	if !prevMax.valid {
+		return maxBruteForce(w.nums, w.begin, w.end)
+	}
+
+	if (w.nums[w.begin-1] == w.nums[w.begin]) && (w.nums[w.end-1] == w.nums[w.end]) {
+		return prevMax
+	}
+
+	if !w.InWindow(prevMax.index) {
+		return maxBruteForce(w.nums, w.begin, w.end)
+	}
+
+	if w.nums[w.end] >= prevMax.value {
+		return WindowMaximum{value: w.nums[w.end], valid: true, index: w.end}
+	}
+
+	return prevMax
+}
+
+func NewWindow(nums []int, k int) *Window {
+	w := Window{}
+	w.nums = nums
+	w.size = k
+	w.numsCount = len(nums)
+	w.begin = 0
+	w.end = k - 1
+
+	if w.end < 0 {
+		return nil
+	}
+	if k > w.numsCount {
+		return nil
+	}
+
+	return &w
+}
+
+type WindowMaximum struct {
+	index int
+	value int
+	valid bool
+}
+
+func MaxSlidingWindow(nums []int, k int) []int {
+	maximums := []int{}
+	var max WindowMaximum
+
+	for w := NewWindow(nums, k); w != nil; w = w.Next() {
+		max = w.Max(max)
+		maximums = append(maximums, max.value)
+	}
+
+	return maximums
+}