Question

#include <algorithm>
#include <stdio.h>
#include <iostream>



int intcomp(int *x,int *y) {  return *x-*y;};
int a[10000];
int main(void){
    int i; int n=0;
     while (scanf("%d",&a[n])!=EOF)
          n++;
     qsort(a,n,sizeof(int),intcomp);
      for (int i=0;i<n;i++)
           printf("%d\n",a[i]);
       return 0;


}

it is just copy of code i have two question it show me that intcomp is incompatible in this code
and also what does intcomp function?
and also what is in windows 7 EOF? how tell program that it reached EOF?

Answer 1

First of all: the question is labeled C++ and you #include <algorithm> and <iostream>, but your code is 100% C.

Martin York already gave the answer how to correct the signature of the function you pass to qsort().

However, the “true”(TM) C++ solution would be to use std::sort<> instead of qsort!

#include <algorithm>    
#include <stdio.h>    

bool intcomp(int a, int b) { return a<b; }
int a[10000];    
int main(void){    
    int n=0;    
     while (scanf("%d",&a[n])!=EOF)    
          n++;    
     std::sort(&a[0], &a[n], intcomp);
      for (int i=0;i<n;i++)    
           printf("%d\n",a[i]);    
       return 0;    
}

Note that incomp() takes ints and not int pointers, and returns a bool. Just like operator<() would.

Also note that in this case, you could forget the intcomp and just use std::sort(&a[0], &a[n]), which will use std::less<>, which will use operator<(int, int).