Project Euler Problem 15

Starting in the top left corner of a 22 grid, there are 6 routes (without backtracking) to the bottom right corner.

How many routes are there through a 2020 grid?

 1 #include <iostream>
 2 using namespace std;
 3 
 4 #define num 41
 5 long long PascalTriangle[num][num];
 6 
 7 void CalcPascalTriangle()
 8 {
 9     PascalTriangle[0][0] = 1;
10     PascalTriangle[1][0] = 1;
11     PascalTriangle[1][1] = 1;
12     for(int i=2; i<num; i++)
13     {
14         for(int j=0; j<=i; j++)
15         {
16             if(j == 0 || j == i)
17             {
18                 PascalTriangle[i][j] = 1;
19             }
20             else
21             {
22                 PascalTriangle[i][j] = PascalTriangle[i-1][j-1] + PascalTriangle[i-1][j];
23             }
24         }
25     }
26 }
27 
28 int main()
29 {
30     CalcPascalTriangle();
31     cout << PascalTriangle[40][20];
32     cin.get();
33 }