#include "stdafx.h"
#include<iostream>
using namespace std;
int main(int argc, char *argv[])
{ float sum(float a=8,float b=10,float c=3);
  float a,b,c;
  cin>>a,b,c;
  cout<<sum(a)<<sum(a,b)<<sum(a,b,c)<<endl;
  return 0;
}
float sum(float a,float b,float c)
{
return a+b+c;
}

[此贴子已经被作者于2023-3-13 22:06编辑过]

搞明白了，谢谢！

#include "stdafx.h"
#include<iostream>
using namespace std;
int main()
{ float sum(float a=8,float b=10,float c=3);
  float a,b,c;
  cin>>a>>b>>c;
  cout<<sum(a)<<","<<sum(a,b)<<","sum(a,b,c);
  return 0;
}
float sum(float a,float b,float c)
{
return a+b+c;
}