Create Cat and Mouse Game

Graphs/Cat and Mouse Game

@@ -0,0 +1,75 @@
+class Solution {
+    public int catMouseGame(int[][] graph) {
+        int N = graph.length;
+        final int DRAW = 0, MOUSE = 1, CAT = 2;
+
+        int[][][] color = new int[50][50][3];
+        int[][][] degree = new int[50][50][3];
+
+        // degree[node] : the number of neutral children of this node
+        for (int m = 0; m < N; ++m)
+            for (int c = 0; c < N; ++c) {
+                degree[m][c][1] = graph[m].length;
+                degree[m][c][2] = graph[c].length;
+                for (int x: graph[c]) if (x == 0) {
+                    degree[m][c][2]--;
+                    break;
+                }
+            }
+
+        // enqueued : all nodes that are colored
+        Queue<int[]> queue = new LinkedList();
+        for (int i = 0; i < N; ++i)
+            for (int t = 1; t <= 2; ++t) {
+                color[0][i][t] = MOUSE;
+                queue.add(new int[]{0, i, t, MOUSE});
+                if (i > 0) {
+                    color[i][i][t] = CAT;
+                    queue.add(new int[]{i, i, t, CAT});
+                }
+            }
+
+        // percolate
+        while (!queue.isEmpty()) {
+            // for nodes that are colored :
+            int[] node = queue.remove();
+            int i = node[0], j = node[1], t = node[2], c = node[3];
+            // for every parent of this node i, j, t :
+            for (int[] parent: parents(graph, i, j, t)) {
+                int i2 = parent[0], j2 = parent[1], t2 = parent[2];
+                // if this parent is not colored :
+                if (color[i2][j2][t2] == DRAW) {
+                    // if the parent can make a winning move (ie. mouse to MOUSE), do so
+                    if (t2 == c) {
+                        color[i2][j2][t2] = c;
+                        queue.add(new int[]{i2, j2, t2, c});
+                    } else {
+                        // else, this parent has degree[parent]--, and enqueue
+                        // if all children of this parent are colored as losing moves
+                        degree[i2][j2][t2]--;
+                        if (degree[i2][j2][t2] == 0) {
+                            color[i2][j2][t2] = 3 - t2;
+                            queue.add(new int[]{i2, j2, t2, 3 - t2});
+                        }
+                    }
+                }
+            }
+        }
+
+        return color[1][2][1];
+    }
+
+    // What nodes could play their turn to
+    // arrive at node (m, c, t) ?
+    public List<int[]> parents(int[][] graph, int m, int c, int t) {
+        List<int[]> ans = new ArrayList();
+        if (t == 2) {
+            for (int m2: graph[m])
+                ans.add(new int[]{m2, c, 3-t});
+        } else {
+            for (int c2: graph[c]) if (c2 > 0)
+                ans.add(new int[]{m, c2, 3-t});
+        }
+        return ans;
+    }
+}