// Returns true if B wins
public static boolean tryFirstMove(GridChar grid, int aKingLoc, int bKingLoc) {
grid.setEntry(aKingLoc, '#');
grid.setEntry(bKingLoc, 'K');
boolean r = true;
while (r) {
// r = findLoserSquares(input.grid);
r = reduceGrid(grid, bKingLoc);
}
for (Direction dir : Direction.values()) {
Integer childIdx = grid.getIndex(bKingLoc, dir);
if (childIdx == null) continue;
char sq = grid.getEntry(childIdx);
if (sq == 'V') {
return true;
}
if (sq == '#' || sq == 'T') {
continue;
}
// int size = 1 + getConnectedSquareCount(grid, childIdx);
if (getConnectedSquareCount(grid, childIdx)) return true;
// if (size % 2 == 0) {
// return true;
// }
}
return false;
}
public static boolean reduceGrid(GridChar grid, final int kingLoc) {
// Create a graph corresponding to grid
GraphInt graph = new GraphInt();
int startingLoc = kingLoc; // getOpenNodeNextToKing(grid, kingLoc);
Set<Integer> visitedNodes = Sets.newHashSet();
LinkedList<Integer> toVisit = new LinkedList<>();
toVisit.add(startingLoc);
while (!toVisit.isEmpty()) {
Integer loc = toVisit.poll();
if (visitedNodes.contains(loc)) continue;
visitedNodes.add(loc);
for (Direction dir : Direction.values()) {
Integer childIdx = grid.getIndex(loc, dir);
if (childIdx == null) continue;
char sq = grid.getEntry(childIdx);
if (sq == '#' || sq == 'K' || sq == 'V' || sq == 'T') continue;
if (loc == kingLoc)
// graph.addOneWayConnection(loc,childIdx);
graph.addConnection(loc, childIdx);
else graph.addConnection(loc, childIdx);
toVisit.add(childIdx);
}
}
ArticulationPoint ap = new ArticulationPoint(graph);
// Find bridges
List<Integer> artPoints = ap.getArticulationPoints();
for (Integer aPoint : artPoints) {
if (aPoint == kingLoc) continue;
Set<Integer> adjNodes = graph.getNeighbors(aPoint);
Set<Integer> isolatedNodes = Sets.newHashSet();
Set<Integer> nonIsolatedNodes = Sets.newHashSet();
adjNodeLoop:
for (Integer adjNode : adjNodes) {
if (isolatedNodes.contains(adjNode) || nonIsolatedNodes.contains(adjNode)) continue;
Set<Integer> nodes =
GraphIntAlgorithms.getConnectedNodesWithoutNode(graph, adjNode, aPoint);
// Isolated set must not contain other articulation points
for (Integer aPointToTest : artPoints) {
if (nodes.contains(aPointToTest)) {
nonIsolatedNodes.addAll(nodes);
continue adjNodeLoop;
}
}
if (!nodes.contains(startingLoc)) {
isolatedNodes = nodes;
break;
}
}
// No suitable isolated set found, continue to next articulation point
if (isolatedNodes == null || isolatedNodes.isEmpty()) continue;
if (isolatedNodes.size() % 2 == 0) {
// All the isolated nodes are traps
for (Integer isoNode : isolatedNodes) {
grid.setEntry(isoNode, 'T');
}
return true;
} else {
// The articulation point itself is a trap, as moving to it means
// the other player can move into an odd numbered field, which is always
// losing
grid.setEntry(aPoint, 'T');
return true;
}
}
return false;
}