import std.algorithm, std.conv, std.range, std.stdio, std.string; import std.container; // SList, DList, BinaryHeap const n = 41, unknown = 0, wall = 1, empty = 2; alias Point!int point; alias Grid!(int, int) igrid; alias Grid!(bool, int) bgrid; void main() { auto g = igrid(n, n); auto p = point(n/2, n/2); auto d = point(0, -1), r = 0; int ask(string c) { import core.stdc.stdlib; if (c != "") { writeln(c); stdout.flush(); } auto s = readln.chomp; if (s == "Merry Christmas!") exit(0); auto r = s.to!int; if (r == 20151224) ask("F"); return r; } auto setKnown(point p, point d, int r) { foreach (i; 1..r+1) g[p + d * i] = empty; g[p + d * (r + 1)] = wall; } auto calcRoute(point p) { auto q = DList!(point[])(), v = bgrid(n, n); q.insertBack([p]); v[p] = true; while (!q.empty) { auto qi = q.front; q.removeFront(); foreach (np; v.sibPoints4(qi.back)) { if (g[np] == unknown) return qi ~ np; if (g[np] == empty && !v[np]) { v[np] = true; q.insertBack(qi ~ np); } } } assert(0); } auto rot(ref point p, ref point d, point td) { while (d != td) { auto r = ask("L"); d = d.predSwitch(point(0, -1), point(-1, 0), point(-1, 0), point(0, 1), point(0, 1), point(1, 0), point(1, 0), point(0, -1)); setKnown(p, d, r); } } auto move(ref point p, ref point d, point[] route) { foreach (np; route[1..$]) { auto td = np - p; rot(p, d, td); if (g[p + d] == wall) return; auto r = ask("F"); p = p + d; setKnown(p, d, r); } } g[p] = empty; r = ask(""); setKnown(p, d, r); for (;;) { auto route = calcRoute(p); move(p, d, route); } } struct Point(T) { T x, y; pure auto opBinary(string op: "+")(Point!T rhs) const { return Point!T(x + rhs.x, y + rhs.y); } pure auto opBinary(string op: "-")(Point!T rhs) const { return Point!T(x - rhs.x, y - rhs.y); } pure auto opBinary(string op: "*")(T a) const { return Point!T(x * a, y * a); } } struct Grid(T, U) { import std.algorithm, std.conv, std.range, std.traits, std.typecons; const sibs4 = [Point!U(-1, 0), Point!U(0, -1), Point!U(1, 0), Point!U(0, 1)]; const sibs8 = [Point!U(-1, 0), Point!U(-1, -1), Point!U(0, -1), Point!U(1, -1), Point!U(1, 0), Point!U(1, 1), Point!U(0, 1), Point!U(-1, 1)]; T[][] m; const size_t rows, cols; mixin Proxy!m; this(size_t r, size_t c) { rows = r; cols = c; m = new T[][](rows, cols); } this(T[][] s) { rows = s.length; cols = s[0].length; m = s; } pure auto dup() const { return Grid(m.map!(r => r.dup).array); } ref pure auto opIndex(Point!U p) { return m[p.y][p.x]; } ref pure auto opIndex(size_t y) { return m[y]; } ref pure auto opIndex(size_t y, size_t x) const { return m[y][x]; } static if (isAssignable!T) { auto opIndexAssign(T v, Point!U p) { return m[p.y][p.x] = v; } auto opIndexAssign(T v, size_t y, size_t x) { return m[y][x] = v; } auto opIndexOpAssign(string op, V)(V v, Point!U p) { return mixin("m[p.y][p.x] " ~ op ~ "= v"); } auto opIndexOpAssign(string op, V)(V v, size_t y, size_t x) { return mixin("m[y][x] " ~ op ~ "= v"); } } pure auto validPoint(Point!U p) { return p.x >= 0 && p.x < cols && p.y >= 0 && p.y < rows; } pure auto points() const { return rows.to!U.iota.map!(y => cols.to!U.iota.map!(x => Point!U(x, y))).joiner; } pure auto sibPoints4(Point!U p) { return sibs4.map!(s => p + s).filter!(p => validPoint(p)); } pure auto sibPoints8(Point!U p) { return sibs8.map!(s => p + s).filter!(p => validPoint(p)); } }