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

#define N		101
#define	MAX_X	1.0
#define IT		1000

int main()
{
	FILE	*fp;
	char	filename[256];
	int		i, j, it = IT;
	int		n = N;
	double	f[N] = {0.0}, fn[N] = {0.0};
	double	dx, x;

	dx = (MAX_X - 0.0)/(double)(N - 1);

	// input initial data
	for(i = 0; i < n; i++){
		x = dx*(double)i;

		f[i] = sin(2.0*M_PI*x);
	}

	// iteration
	for(i = 0; i < it; i++){	
		for(j = 0; j < n; j++){
			if(j == 0)			fn[j] = 0.0;
			else if(j == n - 1)	fn[j] = 0.0;
			else				fn[j] = (f[j - 1] + f[j + 1])/2.0;
		}

		if(i%10 == 0){
			sprintf(filename, "./output/output%03d.dat", i/10);
			if((fp = fopen(filename, "w")) == NULL){
				printf("Fail to file open\n");
				exit(1);
			}

			for(j = 0; j < n; j++)	fprintf(fp, "%lf %lf\n", j*dx, f[j]);
		}

		// update data
		for(j = 0; j < n; j++)	f[j] = fn[j];
	}

	return 0;
}