Checking an array for existing values in C++ - c++

Question

I've got this project I'm working on and it is an rpg game running in the cmd. The player navigates his character through the keyboard and fights enemies to level up and so on. I'm using a 2D array as a grid/map and in the demo version everything is working OK.
Problem: Now, in the more advanced version, I have a class which is used to load game/start new game. The function, that starts a new game, basicly creates .txt save files in which the information is stored. The problem is in the function that generates an enemy list. The enemy characteristics that are being generated, and where the problem is, are the X and Y coordinates. Here is a little bit of code showing the process:
void enemyGenerator(int level)
/* Declare the random generator */
std::default_random_engine generator((unsigned)time(0));
std::uniform_int_distribution<int> coordsX(1, 28); //There are 30 rows, from which the first and the last are border
std::uniform_int_distribution<int> coordsY(1, 48); //50 columns; first and last are border
/* Declare some variables */
int x, y;
bool ready = "False";
/* Check what level is demanded, for example level 1 */
if (level == 1)
{
while(true)
{
//Generate X and Y
x = coordsX(generator);
y = coordsY(generator);
//Now where the problem appears to be
//There will be 600 enemies = 1200 coordinates, so I have declared an array in the .h file
//Called coordinates[1200] = {}; now I want to check it bottom to top if
//the newly generated coordinates are already existing, so:
for (int i = 0; i < 1200; i += 2) //1200 = array size; += 2, because we're checking x & y at once
{
if (x != coordinates[i] && y != coordinates[i + 1] && x + y != 2) //x + y can't be 2, because this is where the player starts (1, 1)
{
if (i == 1198) //If these are the last x and y in the array
{
ready = "True";
break;
//Break the for loop with status ready
}
else
{
continue;
//If it isn't the end of the array simply continue checking
}
}
else
{
ready = "False";
break;
//If the x and y match with the ones in the array, then break with status not ready
}
}
if (ready)
{
break;
//If status is ready then break the loop and assign the rest of the stats
}
else
{
continue;
//If status is not ready then continue generating random values
}
}
//Here I define the values of the stats in private variables of the class
eX = x;
eY = y;
eLVL = 1;
//etc...
}
This is the generating code. And here is how I use it:
void newGame()
....
//I've reached to the point where I want to deploy for example 10 enemies of level 1
for (int i = 0; i < 10; i++)
{
enemyGenerator(1);
//I have an already defined fileWriter (std::fstream; std::ios::out)
fileWriter << eX << " " << eY << " " << eLVL; //<< " " etc...
}
....
Everything seems logical to me, the only illogical thing is that it is not working. The output in enemyList.txt I get is for example 3 5 1 (other stats) 3 5 1 (other stats) 3 5 1 (other stats), you get it.
Question: Can you spot any error? Can you show me the right way? If more of the code is required I can even send you the source file, just for the sake of curing my headache.

Answer 1

The problem there is with your random generator.
You are setting the seed of the generator everytime enemyGenerator() is called with the current time. But since you call enemyGenerator multiple times in the same fraction of a second, the time value is the same, hence the random generator seed is the same everytime, which will give you the same random pattern each successive call.
Either use the same generator for all the calls
...
std::default_random_engine random_generator((unsigned)time(0));
//I've reached to the point where I want to deploy for example 10 enemies of level 1
for (int i = 0; i < 10; i++)
{
enemyGenerator(random_generator, 1);
//I have an already defined fileWriter (std::fstream; std::ios::out)
fileWriter << eX << " " << eY << " " << eLVL; //<< " " etc...
}
....
with the enemyGenerator function is defined as
void enemyGenerator(std::default_random_engine& generator, int level)
or seed your generator with a different value each time.
Edit:
Well it seems it isn't the cause of your problem but you should still consider what I wrote.