# zaiSearch3

 Author zdg Submission date 2011-09-05 16:27:56.757782 Rating 5964 Matches played 2790 Win rate 58.06

Use rpsrunner.py to play unranked matches on your computer.

## Source code:

``````# searching for a past pattern and using it to predict the opponent's next move
# seems like only matching opponent's hands is better than trying to match opponents and own hands
# also only consider patterns after which the opponent wins or ties, since the opponent is more likely to play those hands

# minor tweak of weights

import math
import random

# the hand that beats this hand
beats = {'R':'P', 'P':'S', 'S':'R'}

# returns a weighted random choice of R, P or S
# default with no arguments is uniformly random
def rand_hand(probs=None,sum=None):
if probs is None:
return random.choice(['R', 'P', 'S'])
else:
if sum is None:
sum = probs['R'] + probs['P'] + probs['S']
if sum < 0.5:
return random.choice(['R', 'P', 'S'])
r = random.uniform(0, sum)
if r < probs['R']:
return 'R'
elif r < probs['R'] + probs['P']:
return 'P'
else:
return 'S'

def win(mine, other):
return mine == beats[other]

# finds the length of the match from searchIndex and matchIndex leftward
def searchPatternLengthBackwards(lst, searchIndex, matchIndex, indexLimit, lengthLimit):
length = 0
while searchIndex >= indexLimit and matchIndex >= indexLimit and \
length < lengthLimit and lst[searchIndex] == lst[matchIndex]:
searchIndex -= 1
matchIndex -= 1
length += 1
return length

# calculates the weight of a pattern match based on length and distance
# the distance is from the index where the match is found to the current playing index
def weighPattern(length, lengthLimit, distance, distanceLimit):
if length > 0:
temp = length * length
temp2 = temp * temp
lengthWeight = temp
distanceWeight = ((distanceLimit - distance) / float(distanceLimit)) + 1
return lengthWeight * distanceWeight
else:
return 0

# calculates the weights of the opponent's next move
def calculateWeights(lst, index, distanceLimit, lengthLimit):
indexLimit = index - distanceLimit
weights = {'R':0.0, 'P':0.0, 'S':0.0}
for i in xrange(index - 1, indexLimit - 1, -1):
length = searchPatternLengthBackwards(lst, i, index, indexLimit, lengthLimit)
distance = index - i
# count it only if after that pattern was a tie or a loss
if not win(my_hands[i+1], lst[i+1]):
weight = weighPattern(length, lengthLimit, distance, distanceLimit)
if weight > 0:
weights[lst[i+1]] += weight
return weights

# uses the calculated weights to make a prediction about the opponent's next hand
def predict(lst, index, distanceLimit, lengthLimit,):
weights = calculateWeights(lst, index, distanceLimit, lengthLimit)
return rand_hand(weights)

# start of main code
if input == '':
hands_played = []
my_hands = []
hands = 1

output = rand_hand()
lastHand = output
else:
hands_played.append(input)
my_hands.append(lastHand)

distanceLimit = min(hands - 1, 1000)
lengthLimit = min(hands - 1, 10)

prediction = predict(hands_played, hands - 1, lengthLimit, distanceLimit)
output = beats[prediction]

lastHand = output
hands += 1``````