Google Code Jam Round 1a

omg, 第二题居然要用

The sum of the elements of a single row is twice the sum of the row preceding it. For example, row 0 (the topmost row) has a value of 1, row 1 has a value of 2, row 2 has a value of 4, and so forth. This is because every item in a row produces two items in the next row: one left and one right. The sum of the elements of row n is equal to 2ⁿ.

没想到..没想到….还瞎他妈dfs呢, 算了