From afae42e3a25a429ebb2396d51853c597cd291c9d Mon Sep 17 00:00:00 2001
From: Rostislav Kuratch <kr0st@bioreactor.me>
Date: Thu, 17 Feb 2022 00:56:39 +0200
Subject: [PATCH] "Shortest Subarray with Sum at Least K" hard task No 862
 fixed size sliding window version

---
 862-shortest-subarray-with-sum-at-least-k.go | 56 ++++++--------------
 1 file changed, 17 insertions(+), 39 deletions(-)

diff --git a/862-shortest-subarray-with-sum-at-least-k.go b/862-shortest-subarray-with-sum-at-least-k.go
index 29787e3..6ee31fb 100644
--- a/862-shortest-subarray-with-sum-at-least-k.go
+++ b/862-shortest-subarray-with-sum-at-least-k.go
@@ -5,54 +5,32 @@ func ShortestSubarray(nums []int, k int) int {
 		return -1
 	}
 
-	queue := [100000]int{}
-	queue2 := [100000]int{}
+	wndSz := 1
+	wndStart := 0
 
-	qIterator := &queue
-	q2Iterator := &queue2
-
-	t := qIterator
-
-	qEndPtr := -1
-	qBeginPtr := -1
-
-	q2EndPtr := -1
-	q2BeginPtr := -1
+	wndEnd := 0
+	wndSum := 0
 
+	wndPrevInitialSum := 0
 	lenNums := len(nums)
 
-	for i, n := range nums {
-		if i < lenNums {
-			qEndPtr++
-			qIterator[qEndPtr] = n
-		}
-		if n >= k {
-			return 1
-		}
-	}
+	for wndSz = 1; wndSz <= lenNums; wndSz++ {
 
-	wndSz := 0
-	i := 0
+		wndSum = wndPrevInitialSum + nums[wndSz-1]
+		wndPrevInitialSum = wndSum
+		if wndSum >= k {
+			return wndSz
+		}
 
-	for wndSz = 2; wndSz <= lenNums; wndSz++ {
-		for i = wndSz - 1; i < lenNums; i++ {
-			qBeginPtr++
-			q2EndPtr++
-			q2Iterator[q2EndPtr] = qIterator[qBeginPtr] + nums[i]
-			if q2Iterator[q2EndPtr] >= k {
+		for wndStart = 1; (wndStart + wndSz - 1) < lenNums; wndStart++ {
+
+			wndEnd = wndStart + wndSz - 1
+			wndSum = wndSum - nums[wndStart-1] + nums[wndEnd]
+
+			if wndSum >= k {
 				return wndSz
 			}
 		}
-
-		t = qIterator
-		qIterator = q2Iterator
-		q2Iterator = t
-
-		qBeginPtr = q2BeginPtr
-		qEndPtr = q2EndPtr
-
-		q2BeginPtr = -1
-		q2EndPtr = -1
 	}
 
 	return -1