Unit 8. basic problem in dynamic programming

import random
 
def matrixShortestPath(row, col):
    # sets = [(row+1, col), (row, col+1), (row-1, col), (row, col-1)]
    sets = [(row + 1, col), (row, col + 1)]
    visitedList[row] = visitedList[row] | (2 ** col)
    print(lists[row][col])
 
    # if row == 0 and col == 0:
    #     sets = sets[0:2]
    # elif row == 0:
    #     sets = sets[0:2] + [sets[3]]
    # elif col == 0:
    #     sets = sets[0:3]
    # print(sets)
    max = None
 
    for set in sets:
        row, col = set
        if row < len(lists[0]) and col < len(lists):
            if visitedList[row] & (2 ** col) == 0:
                if lists[row][col] > max:
                    max = lists[row][col]
                    mem = set
 
    if max == None:
        return 0
    row, col = mem
 
    matrixShortestPath(row, col)
 
 
lists = []
size = 15
visitedList = [0 for _ in range(0, size)]
for _ in range(0, size): lists.append([random.randint(1, 100) for _ in range(0, size)])
for list in lists:
    print list
matrixShortestPath(0, 0)
print visitedList
 
visited2x2List = []
for _ in range(0, size):
    visited2x2List.append([])
for i in range(0, size):
    for j in range(0, size):
        if visitedList[i] & 2**j:
            visited2x2List[i].append(1)
        else:
            visited2x2List[i].append(0)
for alist in visited2x2List: print alist