problem18.py

x = [[75],
     [95,64],
     [17,47,82],
     [18,35,87,10],
     [20,04,82,47,65],
     [19,01,23,75,03,34],
     [88,02,77,73,07,63,67],
     [99,65,04,28,06,16,70,92],
     [41,41,26,56,83,40,80,70,33],
     [41,48,72,33,47,32,37,16,94,29],
     [53,71,44,65,25,43,91,52,97,51,14],
     [70,11,33,28,77,73,17,78,39,68,17,57],
     [91,71,52,38,17,14,91,43,58,50,27,29,48],
     [63,66,04,68,89,53,67,30,73,16,69,87,40,31],
     [04,62,98,27,23, 9,70,98,73,93,38,53,60,04,23]]

def dfs(i, j, total=0):
    if i >= len(x):
        return total

    total += x[i][j]

    return max(dfs(i + 1, j, total), dfs(i + 1, j + 1, total))

print dfs(0, 0)