Feat: hw2 done

HW2_pacman/ghostAgents.py

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+from game import Agent
+from game import Actions
+from game import Directions
+import random
+from util import manhattanDistance
+import util
+
+
+class GhostAgent(Agent):
+    def __init__(self, index):
+        self.index = index
+
+    def getAction(self, state):
+        dist = self.getDistribution(state)
+        if len(dist) == 0:
+            return Directions.STOP
+        else:
+            return util.chooseFromDistribution(dist)
+
+    def getDistribution(self, state):
+        "Returns a Counter encoding a distribution over actions from the provided state."
+        util.raiseNotDefined()
+
+
+class RandomGhost(GhostAgent):
+    "A ghost that chooses a legal action uniformly at random."
+
+    def getDistribution(self, state):
+        dist = util.Counter()
+        for a in state.getLegalActions(self.index):
+            dist[a] = 1.0
+        dist.normalize()
+        return dist
+
+
+class DirectionalGhost(GhostAgent):
+    "A ghost that prefers to rush Pacman, or flee when scared."
+
+    def __init__(self, index, prob_attack=0.8, prob_scaredFlee=0.8):
+        self.index = index
+        self.prob_attack = prob_attack
+        self.prob_scaredFlee = prob_scaredFlee
+
+    def getDistribution(self, state):
+        # Read variables from state
+        ghostState = state.getGhostState(self.index)
+        legalActions = state.getLegalActions(self.index)
+        pos = state.getGhostPosition(self.index)
+        isScared = ghostState.scaredTimer > 0
+
+        speed = 1
+        if isScared:
+            speed = 0.5
+
+        actionVectors = [Actions.directionToVector(
+            a, speed) for a in legalActions]
+        newPositions = [(pos[0]+a[0], pos[1]+a[1]) for a in actionVectors]
+        pacmanPosition = state.getPacmanPosition()
+
+        # Select best actions given the state
+        distancesToPacman = [manhattanDistance(
+            pos, pacmanPosition) for pos in newPositions]
+        if isScared:
+            bestScore = max(distancesToPacman)
+            bestProb = self.prob_scaredFlee
+        else:
+            bestScore = min(distancesToPacman)
+            bestProb = self.prob_attack
+        bestActions = [action for action, distance in zip(
+            legalActions, distancesToPacman) if distance == bestScore]
+
+        # Construct distribution
+        dist = util.Counter()
+        for a in bestActions:
+            dist[a] = bestProb / len(bestActions)
+        for a in legalActions:
+            dist[a] += (1-bestProb) / len(legalActions)
+        dist.normalize()
+        return dist