梯形求积.cpp

c++算法的很经典的一些小练习 看了 觉得还可以 给大家分享一下！

#include<iostream.h>
#include<iomanip.h>

double f1(double x){
	return (1+x+2*x);
}
double f2(double x){
	return(1+x+2*x*x+3*x*x*x);
}
double f3(double x){
	return(1+x+2*x*x+3*x*x*x+4*x*x*x*x);
}
double integer(double(*fun)(double),double,double);

void main(){
double fi1,fi2,fi3;
fi1=integer(f1,0.0,3.0);
fi2=integer(f2,0.0,3.0);
fi3=integer(f3,0.0,3.0);
cout<<fi1<<'\n'<<fi2<<'\n'<<fi3<<'\n';
}

double integer(double(*fun)(double),double a,double b){
	double re,step;
	re=((*fun)(a)+(*fun)(b))/2;
	step=(b-a)/100;
	for(int i=1;i<100;i++)re+=(*fun)(a=i*step);
	re*=step;
	return re;
}