C Exercise Example 76
Title:Write a function. When the input n is even, call the function to compute 1/2+1/4+...+1/n; when the input n is odd, call the function 1/1+1/3+...+1/n (using pointer functions).
Program analysis:None.
Example
// Created by www.example.com on 15/11/9.
// Copyright © 2015 Example. All rights reserved.
//
#include<stdio.h>
#include<stdlib.h>
double evenumber(int n);
double oddnumber(int n);
int main()
{
int n;
double r;
double (*pfunc)(int);
printf("Please enter a number:");
scanf("%d",&n);
if(n%2==0) pfunc=evenumber;
else pfunc=oddnumber;
r=(*pfunc)(n);
printf("%lf\n",r);
system("pause");
return 0;
}
double evenumber(int n)
{
double s=0,a=0;
int i;
for(i=2;i<=n;i+=2)
{
a=(double)1/i;
s+=a;
}
return s;
}
double oddnumber(int n)
{
double s=0,a=0;
int i;
for(i=1;i<=n;i+=2)
{
a=(double)1/i;
s+=a;
}
return s;
}
The output result of running the above example is:
请输入一个数字：2 0.500000other extensions