Lattice paths // Project Euler 15

gistfile1.c

#include <stdio.h>
#define SIZE 20

//http://www.robertdickau.com/lattices.html must be known for solution.

int main(void) {
	int i,j;
	long long int grid[SIZE+1][SIZE+1];
	long long sum = 0;
	for(i=0;i<SIZE;i++)
	{
		grid[i][SIZE] = 1;
		grid[SIZE][i] = 1;
	}
	for(i=SIZE-1;i>=0;i--)
	{
		for(j=SIZE-1;j>=0;j--)
		{
			grid[i][j] =grid[i+1][j]+grid[i][j+1];
			sum = grid[i][j];
		}
	}
	printf("%lld",sum);
	return 0;
}