def assignBikes(self, workers, bikes):

M = len(bikes)

N = len(workers)

costs = [[0]*N for _ in xrange(M)]

for i in xrange(M):

for j in xrange(N):

costs[i][j] = abs(workers[j][0]-bikes[i][0])+abs(workers[j][1]-bikes[i][1])

pq = [(0, '0'*M)]

visited = set()

while pq:

cost, state = heapq.heappop(pq)

if state in visited: continue

visited.add(state)

j = state.count('1') #j users have selected bikes

if j>=N: return cost

for i in xrange(M):

if state[i]=='1': continue

nextState = state[:i] + '1' + state[i+1:]

if nextState in visited: continue

heapq.heappush(pq, (cost+costs[i][j], nextState))

return float('inf')