Exercise 1.11---1.12 Pascal's Triangle

1.11 F'ibonates函数的变种，略过。

1.12 题目：

The following pattern of numbers is called Pascal's triangle.

　　　　1

         1    1

      1     2    1

   1     3     3    1

1     4     6     4     1

......

The numbers at the edge of the triangle are all 1, and each number inside the triangle is the sum of the two numbers above it.35 Write a procedure that computes elements of Pascal's triangle by means of a recursive process.

只要按照如下公式计算即可:

　　number_at(row, line)

　　number_at(1,N)=1

　　number_at(N,N)=1

      number_at(N,M)=number_at(N-1,M-1)+number_at(N-1,M)