C++ Lottery program

[london92]

Something is going wrong in my program, it will run, but when I put in any number or character in for an answer, it says it is a correct lottery number.

My program:

#include <iostream>
#include <string>
using namespace std;
int LinearSearch (int [], int, int);


int main()
{

const int Lottery = 10;
int nums [Lottery] = {13579, 26791, 26792, 33445, 55555, 62483, 77777, 79422, 85647, 93121 };
int UserSelection, location;
double USER;

cout << "Type in the lottery number you have purchased now:\n\n ";
cin >> UserSelection;

location = LinearSearch(nums, Lottery, UserSelection);


if ( location >-1 )

cout << "The number you have entered is a direct match!!\n\n YOU HAVE WON!!!\n\n" << location << endl;

else
cout << "We are sorry but the number you have entered was not found, please play again!\n\n ";

cin >> USER;

return 0;

}
int LinearSearch (int list[], int size, int key)
{
int x;

for (x=0; x < size; x++);
{
if (list [x] == key);
return 0;
}

return -1;
}

[Peter_B]

You need to be more careful with where you put your semicolons.
For example in this code:

for (x=0; x < size; x++);
{
if (list [x] == key);
return 0;
}

The semicolons after the for and if statements end those statements. So what happens is this:

1) The 'for' loop runs, but does nothing except increment x
2) We go into the curly brackets, and the 'if' statements runs, but does nothing
3) We reach the 'return 0;' line, which returns 0

So the search function will always return 0 whether or not the lottery number is found.

As an aside, if you had run your code through a debugger you would have spotted this straight away.

[london92]

Thank you for the speedy and very helpful response!

It is running perfect now, cheers.

[Peter_B]

Glad to be of service

Incidentally, a safer way to make the array is like this:

int nums [] = {13579, 26791, 26792, 33445, 55555, 62483, 77777, 79422, 85647, 93121 };
const int Lottery = sizeof(nums)/sizeof(int);

This will automatically make sure that 'Lottery' has the correct value, even if you add or remove values from the array.

Of course, using std::vector would be even better

[london92]

Just made the change, thanks!

Any ideas on how to change this as easily as possible from a linear search to a binary ?

[Lindley]

Just made the change, thanks!

Any ideas on how to change this as easily as possible from a linear search to a binary ?

The standard library contains std::binary_search (if you just want to check existence) or std::lower_bound (if you want to actually get a handle to the element if it exists).

Whether or not you are allowed to use these in your class is a different matter.