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

int main()
{
	FILE *fp1;
	FILE *fp2;
	FILE *fp3;
	FILE *fp4;
	int n;
	double t=0.0,dt=0.01;
	double x1=0.0,v1=0.0;
	double x2=10.0,v2=0.0;
	double x3=20.0,v3=0.0;
	double x4=30.0,v4=0.0;
	double f1(double ,double ,double);
	double f2(double ,double ,double);
	double f3(double ,double ,double);
	double f4(double ,double );
	fp1=fopen("c:\\test1r.dat","w");
	fp2=fopen("c:\\test2r.dat","w");
	fp3=fopen("c:\\test3r.dat","w");
	fp4=fopen("c:\\test4r.dat","w");

	/*ばね定数、質点の質量はすべて１*/

	for (n=0;n<=10000;++n) {
		x4+=v4*dt;		/*４個目*/
		v4+=f4(x3,x4)*dt;
		x3+=v3*dt;		/*３個目*/
		v3+=f3(x2,x3,x4)*dt;
		x2+=v2*dt;		/*２個目*/
		v2+=f2(x1,x2,x3)*dt;
		x1+=v1*dt;		/*１個目*/
		v1+=f1(t,x1,x2)*dt;
		t+=dt;
		fprintf(fp1,"%lf %lf\n",t,x1);
		fprintf(fp2,"%lf %lf\n",t,x2);
		fprintf(fp3,"%lf %lf\n",t,x3);
		fprintf(fp4,"%lf %lf\n",t,x4);
	}
	fclose(fp1);
	fclose(fp2);
	fclose(fp3);
	fclose(fp4);
	return 0;
}
/*１個目*/
double f1(double t,double x1,double x2) {
	return cos(t)-1*(10-fabs(x1-x2));
}
/*２個目*/
double f2(double x1,double x2,double x3) {
	return 1*(10-fabs(x1-x2))-1*(10-fabs(x2-x3));
}
/*３個目*/
double f3(double x2,double x3,double x4) {
	return 1*(10-fabs(x2-x3))-1*(10-fabs(x3-x4));
}
/*４個目*/
double f4(double x3,double x4) {
	return 1*(10-fabs(x3-x4));
}