using System; using System.Linq; using System.Linq.Expressions; using System.Collections.Generic; using Debug = System.Diagnostics.Debug; using StringBuilder = System.Text.StringBuilder; using System.Numerics; using Point = System.Numerics.Complex; using Number = System.Numerics.BigInteger; namespace Program { public class Solver { public void Solve() { var n = sc.Integer(); var a = sc.Integer(n); var H = new HeavyLightDecomposition(n, a); for (int i = 0; i < n - 1; i++) { var f = sc.Integer() - 1; var t = sc.Integer() - 1; H.AddEdge(f, t); } H.Build(0); var q = sc.Integer(); for (int i = 0; i < q; i++) { var f = sc.Integer() - 1; var t = sc.Integer() - 1; var lca = H.GetLCA(f, t); var k = H.depth[f] + H.depth[t] - 2 * H.depth[lca] + 1; if (k < 3) { IO.Printer.Out.WriteLine("NO"); continue; } var A = H.Query(lca, f); var B = H.Query(lca, t); var ans = true; ans &= A; ans &= B; var pf = H.par[f]; var pt = H.par[t]; if (f == lca) { var ptlca = H.GetAncestorAt(t, H.depth[lca] + 1); ans &= ok(a[f], a[t], a[pt]); ans &= ok(a[t], a[lca], a[ptlca]); } else if (t == lca) { var pflca = H.GetAncestorAt(f, H.depth[lca] + 1); ans &= ok(a[pf], a[f], a[t]); ans &= ok(a[f], a[lca], a[pflca]); } else { var ptlca = H.GetAncestorAt(t, H.depth[lca] + 1); var pflca = H.GetAncestorAt(f, H.depth[lca] + 1); ans &= ok(a[pf], a[f], a[t]); ans &= ok(a[f], a[t], a[pt]); ans &= ok(a[pflca], a[lca], a[ptlca]); } if (ans) IO.Printer.Out.WriteLine("YES"); else IO.Printer.Out.WriteLine("NO"); } } public bool ok(int a, int b, int c) { if (a == b || b == c || a == c) return false; if (a < b && b > c) return true; if (a > b && b < c) return true; return false; } public IO.StreamScanner sc = new IO.StreamScanner(Console.OpenStandardInput()); static T[] Enumerate(int n, Func f) { var a = new T[n]; for (int i = 0; i < n; ++i) a[i] = f(i); return a; } static public void Swap(ref T a, ref T b) { var tmp = a; a = b; b = tmp; } } } #region main static class Ex { static public string AsString(this IEnumerable ie) { return new string(System.Linq.Enumerable.ToArray(ie)); } static public string AsJoinedString(this IEnumerable ie, string st = " ") { return string.Join(st, ie); } static public void Main() { var solver = new Program.Solver(); solver.Solve(); Program.IO.Printer.Out.Flush(); } } #endregion #region Ex namespace Program.IO { using System.IO; using System.Text; using System.Globalization; public class Printer : StreamWriter { static Printer() { Out = new Printer(Console.OpenStandardOutput()) { AutoFlush = false }; } public static Printer Out { get; set; } public override IFormatProvider FormatProvider { get { return CultureInfo.InvariantCulture; } } public Printer(System.IO.Stream stream) : base(stream, new UTF8Encoding(false, true)) { } public Printer(System.IO.Stream stream, Encoding encoding) : base(stream, encoding) { } public void Write(string format, T[] source) { base.Write(format, source.OfType().ToArray()); } public void WriteLine(string format, T[] source) { base.WriteLine(format, source.OfType().ToArray()); } } public class StreamScanner { public StreamScanner(Stream stream) { str = stream; } public readonly Stream str; private readonly byte[] buf = new byte[1024]; private int len, ptr; public bool isEof = false; public bool IsEndOfStream { get { return isEof; } } private byte read() { if (isEof) return 0; if (ptr >= len) { ptr = 0; if ((len = str.Read(buf, 0, 1024)) <= 0) { isEof = true; return 0; } } return buf[ptr++]; } public char Char() { byte b = 0; do b = read(); while ((b < 33 || 126 < b) && !isEof); return (char)b; } public string Scan() { var sb = new StringBuilder(); for (var b = Char(); b >= 33 && b <= 126; b = (char)read()) sb.Append(b); return sb.ToString(); } public string ScanLine() { var sb = new StringBuilder(); for (var b = Char(); b != '\n'; b = (char)read()) if (b == 0) break; else if (b != '\r') sb.Append(b); return sb.ToString(); } public long Long() { if (isEof) return long.MinValue; long ret = 0; byte b = 0; var ng = false; do b = read(); while (b != 0 && b != '-' && (b < '0' || '9' < b)); if (b == 0) return long.MinValue; if (b == '-') { ng = true; b = read(); } for (; true; b = read()) { if (b < '0' || '9' < b) return ng ? -ret : ret; else ret = ret * 10 + b - '0'; } } public int Integer() { return (isEof) ? int.MinValue : (int)Long(); } public double Double() { var s = Scan(); return s != "" ? double.Parse(s, CultureInfo.InvariantCulture) : double.NaN; } private T[] enumerate(int n, Func f) { var a = new T[n]; for (int i = 0; i < n; ++i) a[i] = f(); return a; } public char[] Char(int n) { return enumerate(n, Char); } public string[] Scan(int n) { return enumerate(n, Scan); } public double[] Double(int n) { return enumerate(n, Double); } public int[] Integer(int n) { return enumerate(n, Integer); } public long[] Long(int n) { return enumerate(n, Long); } } } #endregion #region HLDecomposition public class HeavyLightDecomposition { public bool ok(int a, int b, int c) { if (a == b || b == c || a == c) return false; if (a < b && b > c) return true; if (a > b && b < c) return true; return false; } public bool Query(int from, int to) { var f = go[from]; var t = go[to]; if (f.id == t.id) { if (from == to) return true; if (pos[to] - pos[from] == 1) { return val[from] != val[to]; } var L = f.seg[pos[from]]; var R = f.seg[pos[to] + 1 - 2]; return (R - L) == 0; } else { var ch = GetAncestorAt(t, f.depth + 1); var med = H[ch]; var ans = true; ans &= Query(med.light.to, to); if (pos[med.light.from] == pos[from]) { } else if (pos[med.light.from] - pos[from] == 1) { ans &= val[from] != val[med.light.from]; } else { var L = f.seg[pos[from]]; var R = f.seg[pos[med.light.from] + 1 - 2]; ans &= (R - L) == 0; } if (pos[med.light.from] != pos[from]) { var A = par[med.light.from]; var B = med.light.from; var C = med.light.to; ans &= ok(val[A], val[B], val[C]); } return ans; } } List[] G; List H = new List(); int[] subTreeSize; public int[] par; int[] pos; int[,] parent; public int[] depth; Node[] go; int[,] hlpar; int[] val; public HeavyLightDecomposition(int n, int[] a) { G = Enumerate(n, x => new List()); subTreeSize = new int[n]; pos = new int[n]; depth = new int[n]; par = new int[n]; parent = new int[20, n]; go = new Node[n]; val = a; } public void AddEdge(int f, int t) { G[f].Add(new Edge(f, t)); G[t].Add(new Edge(t, f)); } #region impl public void Build(int root) { ComputeSubTreeSize(root); Decomposite(new Edge(-1, root), -1, 0, 0); BuildLCA(); BuildHLLCA(); } public void ComputeSubTreeSize(int root) { var stack = new Stack>(); stack.Push(new KeyValuePair(root, -1)); var visit = new bool[G.Length]; while (stack.Any()) { var p = stack.Pop(); var cur = p.Key; var prev = p.Value; if (visit[p.Key]) { foreach (var next in G[cur]) { var to = To(next); if (to != prev) subTreeSize[cur] += subTreeSize[to]; } } else { visit[cur] = true; stack.Push(new KeyValuePair(cur, prev)); subTreeSize[cur]++; foreach (var next in G[cur]) { var to = To(next); if (to != prev) stack.Push(new KeyValuePair(to, cur)); } } } } public void Decomposite(Edge light, int prevId, int d, int lv) { var node = new Node() { light = light, id = H.Count, par = prevId, depth = lv }; H.Add(node); var prev = light.from; var cur = light.to; while (cur != prev) { var next = cur; var max = 0; depth[cur] = d; par[cur] = prev; go[cur] = node; pos[cur] = node.heavy.Count; foreach (var to in G[cur]) { var t = To(to); if (t != prev) max = Math.Max(max, subTreeSize[t]); } foreach (var to in G[cur]) { var t = To(to); if (t == prev) continue; if (max == subTreeSize[t]) { //Debug.WriteLine("{0}->{1}", cur, t); max = 1 << 30; next = t; node.heavy.Add(to); } else Decomposite(to, node.id, d + 1, lv + 1); } prev = cur; cur = next; d++; } node.init(val); } void BuildLCA() { for (int k = 0; k < 19; k++) for (int v = 0; v < G.Length; v++) parent[k, v] = -1; for (int i = 0; i < G.Length; i++) parent[0, i] = par[i]; for (int k = 0; k < 19; k++) { for (int v = 0; v < G.Length; v++) if (parent[k, v] < 0) parent[k + 1, v] = -1; else parent[k + 1, v] = parent[k, parent[k, v]]; } } void BuildHLLCA() { hlpar = new int[8, H.Count]; for (int k = 0; k < 7; k++) for (int v = 0; v < H.Count; v++) hlpar[k, v] = -1; for (int i = 0; i < H.Count; i++) hlpar[0, i] = H[i].par; for (int k = 0; k < 7; k++) { for (int v = 0; v < H.Count; v++) if (hlpar[k, v] < 0) hlpar[k + 1, v] = -1; else hlpar[k + 1, v] = hlpar[k, hlpar[k, v]]; } } public int GetAncestorAt(Node v, int d) { if (v.depth < d) throw new Exception(); for (int i = 0; i < 8; i++) if ((((v.depth - d) >> i) & 1) == 1) v = H[hlpar[i, v.id]]; return v.id; } public int To(Edge t) { return t.to; } public int GetLCA(int u, int v) { if (depth[u] > depth[v]) { var tmp = u; u = v; v = tmp; } for (int k = 0; k < 20; k++) if ((((depth[v] - depth[u]) >> k) & 1) == 1) v = parent[k, v]; if (u == v) return u; for (int i = 19; i >= 0; i--) if (parent[i, u] != parent[i, v]) { u = parent[i, u]; v = parent[i, v]; } return parent[0, u]; } public int GetAncestor(int v, int k) { var to = depth[v] - k; for (int i = 0; i < 20; i++) if ((((depth[v] - to) >> i) & 1) == 1) v = parent[i, v]; return v; } public int GetAncestorAt(int v, int d) { if (depth[v] < d) throw new Exception(); for (int i = 0; i < 20; i++) if ((((depth[v] - d) >> i) & 1) == 1) v = parent[i, v]; return v; } static T[] Enumerate(int n, Func f) { var a = new T[n]; for (int i = 0; i < n; ++i) a[i] = f(i); return a; } #endregion } public class Node { public Edge light; public List heavy = new List(); public int par; public int depth; public int id; public int[] seg; public void init(int[] a) { seg = new int[heavy.Count + 2]; for (int i = 0; i < heavy.Count; i++) { var f = a[heavy[i].from]; var t = a[heavy[i].to]; if (f == t) { seg[i + 1] |= 1; } if (i + 1 < heavy.Count) { if (!ok(f, t, a[heavy[i + 1].to])) seg[i + 1] |= 1; } } for (int i = 1; i <= heavy.Count + 1; i++) seg[i] += seg[i - 1]; } public bool ok(int a, int b, int c) { if (a == b || b == c || a == c) return false; if (a < b && b > c) return true; if (a > b && b < c) return true; return false; } public override string ToString() { var s = new List(); s.Add(light.from); s.Add(light.to); foreach (var e in heavy) s.Add(e.to); return s.AsJoinedString("->"); } } #endregion #region TreeEdge public struct Edge { public int from, to; public Edge(int f, int t) { from = f; to = t; } public override string ToString() { return string.Format("{0}->{1}", from, to); } } #endregion