1. CherubiAI.java
@author: Derek Omuro
@team : No Artificial Flavors

2. Interaction between components
getMove(…)
Iterative-deepening DFS:
explore the tree
examine from leaf to root
Bookkeeping:
remember which moves are best
manage array of values
Evaluation function:
evaluate a board configuration
use for leaf nodes
DFS 1 2 3 …
depth-1
depth
h(x)
Interaction between components

3. Iterative-deepening DFS
public Point getMove(...)
depthLimit = 1
while depthLimit != maxDepth
bestMove = search(depthLimit++)
return bestMove
private Point search(...)
push current state on stack
while stack isn’t empty
if out of time, return null
node = stack.peek()
while node is not a leaf && node has not been visited
stack.push(possible moves of node)
mark node as visited
stack.pop()
// evaluate and bookkeeping... A B C D E F G
Example tree; depth limit is 2

4. Bookkeeping int values[] = private Point search(...)1 2 3
...
max depth
-inf
+inf
±inf
int values[] =
private Point search(...)
node = stack.pop()
int value;
if node is a leaf
value = node.evaluate()
else //node has been visited
value = values[node.depth]
reset values from node.depth to depthLimit
if value is better than values[node.depth-1]
values[node.depth-1] = value
if node.depth == 1
bestMove = node.lastMove A B C 1 5 3 2
max
min

5. Evaluation Function Look at every possible win vector
public int evaluate(...)
value = 0
for every possible win vector
value += score(winVector[])
return value
Update points based on pieces in each win vector
private int score(byte winVector[])
if different pieces in winVector
return 0
else
return 5^(# of pieces)*(±1) O
= 0
= 25
= 5 O O X

6. Putting it all together
Point getMove(…)
Iterative-deepening DFS:
Iterative: keep searching one level deeper
DFS: pop from leaves to root
Bookkeeping:
You only need a single integer array
Update parent based on child
If updating root, save the last move
Evaluation function:
Use to evaluate nodes at depth limit
Look at every possible win vector
DFS 1 2 3 …
depth-1
depth
max depth
h(x)
Interaction between components

7. Coding Tips Do not code everything up at once!
IDDFS: pop from leaf to root
Simple evaluation function
Bookkeeping: manage int values[]
Improve evaluation function
To do:
Alpha-beta pruning
Much more…