Merge pull request neetcode-gh#1938 from kkr2/feat/0743-network-delay…

…-time.go

Create 0743-network-delay-time.go

go/0743-network-delay-time.go

@@ -0,0 +1,71 @@
+type neighbour struct {
+	destination int
+	weight      int
+}
+
+type heapNode struct {
+	distance  int
+	nodeIndex int
+}
+
+func networkDelayTime(times [][]int, n int, k int) int {
+	edgeMap := make(map[int][]neighbour)
+	for _, log := range times {
+		edgeMap[log[0]] = append(edgeMap[log[0]], neighbour{destination: log[1], weight: log[2]})
+	}
+
+	h := &minHeap{heapNode{distance: 0, nodeIndex: k}}
+	heap.Init(h)
+	visited := make(map[int]bool)
+	t := 0
+
+	for !h.isEmpty() {
+		hNode := heap.Pop(h).(heapNode)
+
+		if vis := visited[hNode.nodeIndex]; vis {
+			continue
+		}
+
+		t = max(t, hNode.distance)
+
+		visited[hNode.nodeIndex] = true
+
+		neighbours := edgeMap[hNode.nodeIndex]
+		for _, neigh := range neighbours {
+			if vis := visited[neigh.destination]; !vis {
+				heap.Push(h, heapNode{
+					distance:  neigh.weight + hNode.distance,
+					nodeIndex: neigh.destination})
+			}
+		}
+	}
+
+	if n == len(visited) {
+		return t
+	}
+	return -1
+}
+
+func max(a, b int) int {
+	if a < b {
+		return b
+	}
+	return a
+}
+
+type minHeap []heapNode
+
+func (h minHeap) Len() int           { return len(h) }
+func (h *minHeap) isEmpty() bool     { return len(*h) == 0 }
+func (h minHeap) Less(i, j int) bool { return h[i].distance < h[j].distance }
+func (h minHeap) Swap(i, j int)      { h[i], h[j] = h[j], h[i] }
+
+func (h *minHeap) Push(x interface{}) {
+	*h = append(*h, x.(heapNode))
+}
+
+func (h *minHeap) Pop() interface{} {
+	l := (*h)[len(*h)-1]
+	*h = (*h)[:len(*h)-1]
+	return l
+}