sol1.c File Reference

Problem 15 solution More...

#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>

Include dependency graph for sol1.c:

Functions
unsigned long long	number_of_paths (int N)
	At every node, there are 2 possible ways to move -> down or right. More...
int	main (int argc, char **argv)
	Main function. More...

Detailed Description

Problem 15 solution

Author

Krishna Vedala

Function Documentation

main()

int main	(	int	argc,
		char **	argv
	)

Main function.

{
    int N = 20;
 
    if (argc == 2)
        N = atoi(argv[1]);
 
    printf("Number of ways to traverse diagonal of %dx%d grid = %llu\n", N, N,
           number_of_paths(N));
 
    return 0;
}

Here is the call graph for this function:

number_of_paths()

unsigned long long number_of_paths

(

int

N

)

At every node, there are 2 possible ways to move -> down or right.

Since it is a square grid, there are in all, 2N steps with N down and N right options, without preference for order. Hence, the path can be be traced in N out of 2N number of ways. This is the same as binomial coeeficient.

{
    unsigned long long path = 1;
    for (int i = 0; i < N; i++)
    {
        path *= (N << 1) - i;
        path /= i + 1;
    }
 
    return path;
}