The result wasn't what I expected what i expect - c++

Question

The problem is to delete all the biggest number
for example:
cin: 1 2 3 4 5
cout: 1 2 3 4
cin: 5 1 2 3 5
cout: 1 2 3
cin: 5 5 1 2 5
cout: 1 2
cin: 5 5 5 1 5
cout: 1
and here is where things go wrong:
whenever my biggest number locate in the first and the last location with other location, the code print out the wrong result
please look at these example for better understanding:
cin: 5 5 1 2 5
expected cout: 1 2
but instead it cout: 5 1
cin: 5 5 1 5 5
expected cout: 1
but instead it cout: 5
I think the problem occured in the delete function but I can't figure out what went wrong no matter how many time i rechecked, i would be very happy if someone can help me solve this problem.
and sorry for my sloppy writing and bad english
here is my code:
#include <iostream>
using namespace std;
void Insert(int a[] ,int n)
{
for (int i=0; i<n; i++)
{
cout << "a[" << i << "]= ";
cin >> a[i];
}
}
void Delete(int a[], int n, int Biggestt)
{
int BiggestLocation;
for (int i=0; i<n-1; i++)
{
if (a[i]==Biggestt)
{
BiggestLocation=i;
}
}
for (int i=BiggestLocation; i<n-1; i++)
{
a[i]=a[i+1];
}
}
int Biggest(int a[],int n)
{
int Biggesttt=a[0];
for (int i=0; i<n; i++)
{
if (Biggesttt<a[i])
{
Biggesttt=a[i];
}
}
return Biggesttt;
}
void PrintOut(int a[],int n)
{
for (int i=0; i<n; i++)
{
cout << a[i] << " ";
}
}
int main()
{
int n,OriginalCount;
int Count=0;
cout << "Insert n: ";
cin >>n;
int a[100];
Insert(a,n);
int Biggestttt=Biggest(a,n);
for (int i=0; i<n-1; i++)
{
if(a[i]==Biggestttt)
{
Count++;
}
}
OriginalCount=Count;
while(Count!=0)
{
{
Delete(a,n,Biggestttt);
}
Count--;
}
if (a[n-1]==Biggestttt && OriginalCount==0)
{
PrintOut(a,n-1);
}
else if (a[n-1]!=Biggestttt && OriginalCount!=0)
{
PrintOut(a,n-OriginalCount);
}
else if (a[n-1]==Biggestttt && OriginalCount!=0)
{
PrintOut(a,n-OriginalCount-1);
}
return 0;
}

Answer 1

You are not far off. You biggest issues have to do with using void function () for all your functions. By using void as the type, you lose the ability to return valid (and needed) information.
For example in void Delete(int a[], int n, int Biggestt) the number of elements that remain in a[] will change as each element matching the Biggestt are removed from the array -- but you have no way of returning the final number of elements in the array after the removals take place. You can either change your return type from void to int and return an updated n, or you can pass n as a pointer parameter so when it is update within the function, its updated value is available back in the calling function when Delete() returns.
Additionally, your logic in main() is quite jumbled. You already have functions created to handle your needs, so main() should be relatively clean and have no more than a couple of variables to deal with. You could do something like:
int main (void)
{
int n, b,
a[MAXINT];
cout << "Insert n: ";
if (!(cin >> n)) { /* validate ALL user input */
cerr << "(invalid conversion or user canceled)\n";
return 1;
}
Insert (a, n); /* insert all array values */
cout << "original: "; /* output the original */
PrintOut (a, n);
b = Biggest (a, n); /* find the biggest number in the arry */
Delete (a, &n, b); /* delete all occurrences in array */
cout << "big deleted: "; /* output array with biggest removed */
PrintOut (a, n);
return 0;
}
(note: since your Delete() function has been left void a pointer to n was passed as a parameter so the final value of n after element deletion will be available back in the calling function (main() here))
Putting it altogether and making adjustments to the logic in Delete(), you could do something like the following:
#include <iostream>
using namespace std;
#define MAXINT 100
void Insert (int a[], int n)
{
for (int i=0; i<n; i++)
{
cout << "a[" << i << "]= ";
cin >> a[i];
}
}
void Delete(int *a, int *n, int Biggestt)
{
for (int i = 0; i < *n;)
{
if (*n > 1 && a[i] == Biggestt)
{
for (int j = i + 1; j < *n; j++)
a[j-1] = a[j];
(*n)--; /* if biggest removed, decrement n */
}
else
i++; /* only advance if biggest not removed at index */
}
}
int Biggest(int a[],int n)
{
int Biggesttt=a[0];
for (int i=1; i<n; i++)
{
if (Biggesttt<a[i])
{
Biggesttt=a[i];
}
}
return Biggesttt;
}
void PrintOut(int a[],int n)
{
for (int i=0; i<n; i++)
{
cout << " " << a[i];
}
cout << '\n';
}
int main (void)
{
int n, b,
a[MAXINT];
cout << "Insert n: ";
if (!(cin >> n)) { /* validate ALL user input */
cerr << "(invalid conversion or user canceled)\n";
return 1;
}
Insert (a, n); /* insert all array values */
cout << "original: "; /* output the original */
PrintOut (a, n);
b = Biggest (a, n); /* find the biggest number in the arry */
Delete (a, &n, b); /* delete all occurrences in array */
cout << "big deleted: "; /* output array with biggest removed */
PrintOut (a, n);
return 0;
}
Exmple Use/Output
$ ./bin/remove_biggest
Insert n: 5
a[0]= 5
a[1]= 1
a[2]= 2
a[3]= 3
a[4]= 5
original: 5 1 2 3 5
*n: 3
*n: 3
*n: 3
big deleted: 1 2 3
$ ./bin/remove_biggest
Insert n: 4
a[0]= 5
a[1]= 5
a[2]= 1
a[3]= 5
original: 5 5 1 5
*n: 1
big deleted: 1
What if all number in a[...] are the same? You have to be able to handle that case. The logic in Delete() now retains 1 number if the are all the same number. You may also choose to leave them ALL as there is no Biggestt. The are simultaneously the largest and smallest at the same time. How you handle it is up to you.
$ ./bin/remove_biggest
Insert n: 4
a[0]= 5
a[1]= 5
a[2]= 5
a[3]= 5
original: 5 5 5 5
*n: 1
big deleted: 5
If they were all the same Big number we just deleted all of them leaving 1 as it is also the minimum.
Using a Reference int& n Instead of a Pointer
In response to your comment and the suggestion by Fei Xiang, C++ allows you to pass a reference to n in Delete() instead of a pointer to ensure changes to n are visible back in the calling function (main here). The crux of the matter is when you simply pass a parameter to a function, the function receives a copy and any changes made to the variable within the function are lost on return. C++ provides a reference (e.g. int& n) which essentially passes an alias to the original and any changes made to the reference are changes made to the original. This is a refinement over passing the address of the variable because it does avoid having to dereference the pointer.
Using a reference, Delete() could be re-written as follows:
void Delete (int *a, int& n, int Biggestt)
{
for (int i = 0; i < n;)
{
if (n > 1 && a[i] == Biggestt)
{
for (int j = i + 1; j < n; j++)
a[j-1] = a[j];
n--; /* if biggest removed, decrement n */
}
else
i++; /* only advance if biggest not removed at index */
}
}
The call to Delete() in main() would be:
Delete (a, n, b); /* delete all occurrences in array */
And you have gotten rid of the so-called '*' marks :) (that Fei)

Answer 2

#include <iostream>
using namespace std;
void Insert(int a[] ,int n)
{
for (int i=0; i<n; i++)
{
cout << "a[" << i << "]= ";
cin >> a[i];
}
}
void Delete(int a[], int n, int Biggestt)
{
int BiggestLocation;
for (int i=0; i<n-1; i++)
{
if (a[i]==Biggestt)
{
a[i]=-1;
}
}
for (int i=1; i<n; i++)
{
if(a[i-1]==-1)
a[i-1]=a[i];
}
}
int Biggest(int a[],int n)
{
int Biggesttt=a[0];
for (int i=0; i<n; i++)
{
if (Biggesttt<a[i])
{
Biggesttt=a[i];
}
}
return Biggesttt;
}
void PrintOut(int a[],int n)
{
for (int i=0; i<n; i++)
{
cout << a[i] << " ";
}
}
int main()
{
int n,OriginalCount;
int Count=0;
cout << "Insert n: ";
cin >>n;
int a[100];
Insert(a,n);
int Biggestttt=Biggest(a,n);
for (int i=0; i<n-1; i++)
{
if(a[i]==Biggestttt)
{
Count++;
}
}
OriginalCount=Count;
while(Count!=0)
{
{
Delete(a,n,Biggestttt);
}
Count--;
}
if (a[n-1]==Biggestttt && OriginalCount==0)
{
PrintOut(a,n-1);
}
else if (a[n-1]!=Biggestttt && OriginalCount!=0)
{
PrintOut(a,n-OriginalCount);
}
else if (a[n-1]==Biggestttt && OriginalCount!=0)
{
PrintOut(a,n-OriginalCount-1);
}
return 0;
}
TRY THIS CODE.
Just equate all the instances of biggest number to -1 and later overwrite them with the neighboring elements which are not equal to -1.