add new solutions

solutions/14/q1466/solution.go

@@ -0,0 +1,67 @@
+package q1466
+
+import "math"
+
+func walk(connections [][2][]int, minFlips []int32, node int) {
+	mf := minFlips[node]
+
+	// Walk no-flip-needed
+	for _, n := range connections[node][1] {
+		if mf < minFlips[n] {
+			minFlips[n] = mf
+			walk(connections, minFlips, n)
+		}
+	}
+
+	// Walk flip-needed
+	for _, n := range connections[node][0] {
+		if mf+1 < minFlips[n] {
+			minFlips[n] = mf + 1
+			walk(connections, minFlips, n)
+		}
+	}
+}
+
+func collect(connections [][2][]int, minFlips []int32, node int, visited []bool) int32 {
+	mf := minFlips[node]
+	var sum int32
+
+	for _, n := range connections[node][1] {
+		if !visited[n] && mf == minFlips[n] {
+			visited[n] = true
+			sum += collect(connections, minFlips, n, visited) - mf
+		}
+	}
+
+	for _, n := range connections[node][0] {
+		if !visited[n] && mf+1 == minFlips[n] {
+			visited[n] = true
+			sum += collect(connections, minFlips, n, visited) - mf
+		}
+	}
+
+	return sum + mf
+}
+
+func minReorder(n int, connections [][]int) int {
+	conns := make([][2][]int, n)
+	for i := range connections {
+		from, to := connections[i][0], connections[i][1]
+		conns[from][0] = append(conns[from][0], to)
+		conns[to][1] = append(conns[to][1], from)
+	}
+
+	minFlips := make([]int32, n) // minimum flips to reach node n
+	minFlips[0] = math.MaxInt32
+	for i := 1; i < len(minFlips); i *= 2 {
+		copy(minFlips[i:], minFlips[:i])
+	}
+	minFlips[0] = 0
+
+	walk(conns, minFlips, 0)
+
+	visited := make([]bool, n)
+	return int(collect(conns, minFlips, 0, visited))
+}
+
+var _ = minReorder