4 Sum

class Solution:    # @return a list of lists of length 4, [[val1,val2,val3,val4]]    def fourSum(self, num, target):        numLen, res, dict = len(num), set(), {}        if numLen < 4: return []        num.sort()        for p in range(numLen):            for q in range(p+1, numLen):                 if num[p]+num[q] not in dict:                    dict[num[p]+num[q]] = [(p,q)]                else:                    dict[num[p]+num[q]].append((p,q))        for i in range(numLen):            for j in range(i+1, numLen-2):                T = target-num[i]-num[j]                if T in dict:                    for k in dict[T]:                        if k[0] > j: res.add((num[i],num[j],num[k[0]],num[k[1]]))        return [list(i) for i in res]