Can anyone please tell me what this error means?

[Zoe Zibble]

Write your question here.
I met tons of error , anyone help me?

  #include <iostream>
using namespace std;
int main()
{
  int n;
  cin>>n;
  int trans[n];
  int price[n];
  int t[n];
  for(int i=1;i<=n;i++){
    cin>>trans[i];
    cin>>price[i];
    cin>>t[i];
  }
  int coupon_valid[n];
  int coupon_t[n];
  int actual_price[n];
  for(int j=1;j<=n;j++){
    if(j==1){
      actual_price[j]==price[j];
// to demonstrate the validation time and price of the coupon when using bus   
    }else if(trans[j]==0){
//      coupon_t[j]=t+45;
//      coupon_valid[j]=price[j];
//    }
      for(int k=j-1;k>=1;k--){
//        if(trans[k]==1 && coupon_t[k-1]>t[k] && coupon_valid[k-1]>price[k]){
        if(trans[k]==1 && coupon_t[k-1]>t[k] && price[k]>price[j]){
  //      actual_price==0;
        coupon_valid[j]=price[k];
        }
      }
    }else {
      actual_price[j]=price[j];
    }
      
    }
  }
  int total=0;
  for(int q=1;q<=n;q++){
    total=total+actual_price[q];
  }
  cout<<total;
	return 0;
}

[Handy Andy]

hello Steve1029,

What error???

Copy and post the error messages that your compiler gave you. That would be a good start.

Andy

Edit: typo.

[Handy Andy]

Hello Steve1029,

Looking at your code the first thing I notice is the use of {}s. Whatever style you choose, https://en.wikipedia.org/wiki/Indentation_style , be consistant. Although the compiler does not care the person reading it does. Personally I like the "alman" style.

A few blank lines also help in readability.

Variable length Arrays, or (VLAs) are not allowed in C++, as far as I know. The compiler needs to know the size of the array at compile time to set aside the correct space on the stack for the array. What is in the []s needs to be a variable defined as a constant or an actual number. If you need to input the size of the array you could create a dynamic array on the heap with the keyword "new".

As I understand it C and some very old C++ compilers do allow VLAs.

The comments in the program should be a good start.

#include <iostream>

using namespace std;  // <--- Best not to use.
// A recent post that is worth reading. http://www.cplusplus.com/forum/beginner/258335/

int main()
{
	int n;
	// <--- Needs a prompt.
	cin >> n;

	int trans[n]; // <--- VLAs not allowed in C++.
	int price[n];
	int t[n];

	for (int i = 1; i <= n; i++)
	{
		std::cout << "\n Enter trans: ";
		cin >> trans[i];

		// <--- Needs a prompt.
		cin >> price[i];

		// <--- Needs a prompt.
		cin >> t[i];
	}

	int coupon_valid[n];
	int coupon_t[n];
	int actual_price[n];

	for (int j = 1; j <= n; j++)
	{
		if (j == 1)
		{
			actual_price[j] == price[j];
			// to demonstrate the validation time and price of the coupon when using bus   
		}
		else if (trans[j] == 0)
		{
			//      coupon_t[j]=t+45;
			//      coupon_valid[j]=price[j];
			//    }
			for (int k = j - 1; k >= 1; k--)
			{
				//        if(trans[k]==1 && coupon_t[k-1]>t[k] && coupon_valid[k-1]>price[k]){
				if (trans[k] == 1 && coupon_t[k - 1] > t[k] && price[k] > price[j])
				{
					//      actual_price==0;
					coupon_valid[j] = price[k];
				}
			}
		}
		else
		{
			actual_price[j] = price[j];
		}

	}
}

int total = 0; // <--- Are these lines a function or should it be part of main?

for (int q = 1; q <= n; q++)
{
	total = total + actual_price[q];
}

cout << total;

return 0;
}

Changing the arrays to vectors would be a good start. Also you could make use of "n", should be a better name not a single letter, to give the vector a size when defined.

Your for loops start at (1), but C++ is zero based, so you are missing element (0) zero of your arrays.

Be careful using "<=" in your for loops. Sometimes it can give you one extra loop that you do not want.

This is what I see without compiling the code. Compiled it gave me 31 errors and 4 warnings. most of which had to do with VLAs and the code at the end after "main".

Andy

[againtry]

@OP
This runs and my changes are shown. I have no idea if it makes any sense what you are doing. All fixed - green tick! :)

#include <iostream>
using namespace std;
int main()
{
    int n;
    std::cout << "Enter n: "; // <--
    cin>>n;
    int trans[n];
    int price[n];
    int t[n];
    for(int i=1;i<=n;i++)
    {
        std::cout << "Enter trans: "; // <--
        cin>>trans[i];
        std::cout << "Enter price: "; // <--
        cin>>price[i];
        std::cout << "Enter trans: "; // <--
        cin>>t[i];
    }
    int coupon_valid[n];
    int coupon_t[n];
    int actual_price[n];
    for(int j=1;j<=n;j++)
    {
        if(j==1)
        {
            actual_price[j]==price[j]; // <-- THIS ISN"T USED
            // to demonstrate the validation time and price of the coupon when using bus
        }
        else if(trans[j]==0)
        {
            //      coupon_t[j]=t+45;
            //      coupon_valid[j]=price[j];
            //    }
            for(int k=j-1;k>=1;k--)
            {
                //        if(trans[k]==1 && coupon_t[k-1]>t[k] && coupon_valid[k-1]>price[k]){
                if(trans[k]==1 && coupon_t[k-1]>t[k] && price[k]>price[j])
                {
                    //      actual_price==0;
                    coupon_valid[j]=price[k];
                }
            }
        }
        else
        {
            actual_price[j]=price[j];
        }
        
    }
    //} // <--
    int total=0;
    for(int q=1;q<=n;q++)
    {
        total=total+actual_price[q];
    }
    cout<<total;
    return 0;
}

[Zoe Zibble]

Gee,thanks!

[againtry]

Don't forget that you can't make an array like that, in your line 5

If you don't know about dynamic arrays just write

const int SIZE = 100;
trans[SIZE]{0};
price[SIZE]{0}; 

etc for all the other arrays you might have. And then provided n is less than 100 you'll have enough arrays elements to do the job.

If your problem is solved please sign off the thread with a green tick.