public void Stress() { var mt = MTRandom.Create(); for (int phase = 0; phase < 10000; phase++) { int n = mt.Next(2, 21); int m = mt.Next(1, 101); var(s, t) = mt.NextPair(0, n); if (mt.NextBool()) { (s, t) = (t, s); } var g = new MfGraphInt(n); for (int i = 0; i < m; i++) { int u = mt.Next(0, n); int v = mt.Next(0, n); int c = mt.Next(0, 10001); g.AddEdge(u, v, c); } int flow = g.Flow(s, t); int dual = 0; var cut = g.MinCut(s); var vFlow = new int[n]; foreach (var e in g.Edges()) { vFlow[e.From] -= e.Flow; vFlow[e.To] += e.Flow; if (cut[e.From] && !cut[e.To]) { dual += e.Cap; } } dual.Should().Be(flow); vFlow[s].Should().Be(-flow); vFlow[t].Should().Be(flow); for (int i = 0; i < n; i++) { if (i == s || i == t) { continue; } vFlow[i].Should().Be(0); } } }
static void Solver(TextReader reader, TextWriter writer) { int[] nm = reader.ReadLine().Split().Select(int.Parse).ToArray(); (int n, int m) = (nm[0], nm[1]); char[][] grid = new char[n][]; for (int i = 0; i < n; i++) { grid[i] = reader.ReadLine().ToCharArray(); } var g = new MfGraphInt(n * m + 2); int s = n * m, t = n * m + 1; for (int i = 0; i < n; i++) { for (int j = 0; j < m; j++) { if (grid[i][j] == '#') { continue; } int v = i * m + j; if ((i + j) % 2 == 0) { g.AddEdge(s, v, 1); } else { g.AddEdge(v, t, 1); } } } for (int i = 0; i < n; i++) { for (int j = 0; j < m; j++) { if ((i + j) % 2 != 0 || grid[i][j] == '#') { continue; } int v0 = i * m + j; if (i != 0 && grid[i - 1][j] == '.') { int v1 = (i - 1) * m + j; g.AddEdge(v0, v1, 1); } if (j != 0 && grid[i][j - 1] == '.') { int v1 = i * m + (j - 1); g.AddEdge(v0, v1, 1); } if (i + 1 < n && grid[i + 1][j] == '.') { int v1 = (i + 1) * m + j; g.AddEdge(v0, v1, 1); } if (j + 1 < m && grid[i][j + 1] == '.') { int v1 = i * m + (j + 1); g.AddEdge(v0, v1, 1); } } } writer.WriteLine(g.Flow(s, t)); MfGraph <int, IntOperator> .Edge[] edges = g.Edges(); foreach (MfGraph <int, IntOperator> .Edge e in edges) { if (e.From == s || e.To == t || e.Flow == 0) { continue; } int i0 = e.From / m, j0 = e.From % m; int i1 = e.To / m, j1 = e.To % m; if (i0 == i1 + 1) { grid[i1][j1] = 'v'; grid[i0][j0] = '^'; } else if (j0 == j1 + 1) { grid[i1][j1] = '>'; grid[i0][j0] = '<'; } else if (i0 == i1 - 1) { grid[i0][j0] = 'v'; grid[i1][j1] = '^'; } else { grid[i0][j0] = '>'; grid[i1][j1] = '<'; } } for (int i = 0; i < n; i++) { writer.WriteLine(grid[i]); } }