solved

[Volatile Pulse]

for (int i = 0; i < ARRAY_SIZE; i ++)
   for (int j = i + 1; j < ARRAY_SIZE; j ++)
      // number found
      if (myArray[i] == myArray[j])
         std::cout << "Duplicate number found: " << myArray[i];

[KingJ]

This is what I came up with still running into some trouble

int main(){
int myArray[1000001];
//For Loop to check through the Array
for (int i = 1; i < 1000000; i++)
for (int j = i + 1; j < 1000000; j ++)
{
if (myArray[i] == myArray[j])
{
cout << "Duplicate number found: " << myArray[i];
break;
}
}

}

[Volatile Pulse]

First off, you're creating an array size of 1,000,001. Why? The instructions only say the array will hold numbers 1-1,000,000. It doesn't say that it will be 1,000,000 values in that array.

Also, you're not including all possible choices. int i should start at 0, not 1. Also, what sort of trouble are you having?

[KingJ]

Just realized that, must've slipped my mind so I tweaked my program and its working fine now..... Thanks for your help.

[TheIdeasMan]

This looks like homework to me.

Apologies to Volatile Pulse - I am going to have a go here - hope you don't mind.
If it is homework, I doubt that it should be answered with 4 lines of code!!

The problem is that if the array size is 1 million, the nested for loops will run 1 trillion times. If you have a computer that can process 1 billion items per second on this data, then it will still take 1000 seconds to execute - which is 16 minutes 40 seconds - quite long don't you think.

Also if it is homework, I would have thought that the teacher would have given reasonable instructions on how to go about doing the assignment. I am sure there would have been more to it than a couple of for loops. I think the fact that the amount of data is 1 million was done on purpose, so it would force the students to use a decent data structure to hold the data, thereby giving a much better algorithm to find the answer.

So to the OP, can you come with a data structure to hold this info and make it easier to find the answer?

Are you allowed to use C++ STL containers, or do you have code the whole thing yourself?


Edit:

Your array doesn't have any data in it - Where is this coming from?

[TheIdeasMan]

It's frowned upon to delete stuff out of your post like that.

If it's solved, just mark it as solved.

If you thought it was a silly question, then don't worry everyone starts somewhere!!

[Dns]

You should've keep your question even after it solved for other people to learn, man!

[Peter87]

The original question was:

KingJ wrote:

Array Help
Given an array of integers between 1 and 1,000,000. One integer is in the array twice. How do I find the duplicate number??