算法——Runge_Kutta算法

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


double xi[100];
double yi[100];
/*double f(double x,double y)
{
    double z;
    z=-x*(y*y);
    return z;
}*/
/*
double f(double x,double y)
{
    double z;
    z=y-2.0*x/y;
    return z;
}
*/
/*double f(double x,double y)
{
    double z=-y+x+1;
    return z;
}*/
double f(double x,double y)
{
    double z=(-y+x*x+4*x-1)*0.5;
    return z;
}
void Runge_Kutta(double x0,double y0,double h,double xn)
{
     int i=0,n;
     double k1,k2,k3,k4;
     n=(int)((xn-x0)/h+0.0000001);
     xi[0]=x0;
     yi[0]=y0;
     for(i=1;i<n;