I'm trying to write a program that randomly selects three items from an array that contains five different fruits or vegetables and then display this randomly selected content to the user. Now I'm having trouble understanding why my output is not consistent because sometimes when I run it I'll get something like this:
This bundle contains the following:
Broccoli
With the first two items missing and sometimes I'll get this:
This bundle contains the following:
Tomato
Tomato
Tomato
This is the portion of the code I'm currently having trouble with:
void BoxOfProduce::output() {
cout << "This bundle contains the following: " << endl;
// Use this so it will be truly random
srand(time(0));
for (int f = 0; f < 3; f++) {
// Here were making the random number
int boxee = rand() % 5;
// Adding the content to the box
Box[f] = Box[boxee];
// Now were calling on the function to display the content
displayWord(boxee);
} // End of for loop
} // End of output()
void BoxOfProduce::displayWord(int boxee) {
cout << Box[boxee] << endl;
}
int main() {
BoxOfProduce b1;
b1.input();
b1.output();
Can someone help me understand why i'm getting this output? Thanks!
Don't do it like you are doing it :)
Like #John3136 pointed out, you are messing up your Box variable..
void BoxOfProduce::output()
{
srand(time(NULL)); //keep in mind that this is NOT entirely random!
int boxee = rand() % 5;
int i = 0;
while(i<5)
{
boxee = rand() % 5;
cout<<Box[boxee]<<endl; //this line might be wrong, my point is to print element of your array with boxee index
i++;
}
}
Box[f] = Box[boxee]; is changing the contents of the "Box" you are picking things out of. If the first random number is 3, item 3 gets copied to item 0, so now you have twice as much chance of getting that item the next time through the loop...
You are overwriting the elements of your array with randomly selected item.
Box[f] = Box[boxee];
For eg: If boxee=1 and f=0, it will overwrite element at index 0 with 1, while at same time element at index 1 is same leaving two copies of same item.
Use :std:random_shuffle instead.
Related
I am having trouble generating random fruit for my Snake game. (I am very new to programming and this is my first language).
When I run my code all works fine so far (except from some minor issues). I'm using Visual Studio C++ in an empty project. Here is my full code (I'm not displaying my #includes):
using namespace std;
bool gameOver = false;
int gameScore;
int fruitX;
int fruitY;
string bGameW = "###########";
string bGameL = "# #\n";
class gameStart
{
public:
void start()
{
cout << bGameW;
cout << bGameL;
cout << bGameL;
cout << bGameL;
cout << bGameL;
cout << bGameL;
cout << bGameL;
cout << bGameL;
cout << bGameL;
cout << bGameW;
}
void generateFruit()
{
srand(time(NULL));
fruitX = rand() % 21;
fruitY = rand() % 21;
bGameW.insert(fruitX, "F");
bGameL.insert(fruitY, "F");
}
void clearscreen()
{
system("cls");
}
private:
};
int main ()
{
gameStart gameObj;
gameObj.generateFruit();
gameObj.clearscreen();
gameObj.start();
return 0;
}
To generate the random the random fruit for the string. I use a string to make the game board, then I create random values for the fruit (X and Y) then I append them into my game board.
But the issue is: I want to make only one fruit with a random X and Y and append it into my game board to display it. But my current code is this:
bGameW.insert(fruitX, "F");
bGameL.insert(fruitY, "F");
This code makes 2 fruits with 1 at a random X and 1 at a random Y. I want to turn these 2 fruits into 1 fruit, with 1 random X and 1 random Y.
There's a whole host of things worth commenting on. Here goes:
bGameW has no \n
bGameW and bGameL are 10 and 11 characters long (both with be 11 after you add the other \n). Your RNG is generating numbers between 0 and 20... if you ever generate a number > 11 (and you will), Bad Things will happen (and probably have).
Snake games like this let you eat multiple fruit, which is why people brought up the whole "don't call srand more than once" thing, as you'll be calling generate fruit every time someone eats the old one. OTOH, that mostly removes the "calling srand multiple times per second can return the same value" problem too.
Rather than writing out those two lines, bGameW and bGameL, I recommend that you build a character array that holds your entire game display (NOT your game state, just the display of that state). You then clear it and redraw it every move. You'll need a game area, walls, something that tracks where your snake is, and the current fruit. You then 'render' all these things into your character-array-game-display. Don't forget to clear it every time you redraw it or you'll get all kinds of problems.
Rather than redrawing everything, you could use something like the "curses" library to clear and redraw specific character locations on the screen. You'd then face problems 'clearing' and redrawing different spots.
As far as programming style goes, you will find that so called "magic numbers" (like 21 in your case) can lead to bugs. What people generally do instead is to define a const with the appropriate value, and then define things in terms of that const.
// constants are often named in ALL_UPPER_CASE_WITH_UNDERSCORES
// to help you recognize them.
const int PLAY_AREA_HEIGHT = 10;
const int PLAY_AREA_WIDTH = 10;
const char EMPTY_PLAY_SQUARE = '.';
// have you learned about 2d arrays yet? Arrays at all?
char playAreaDisplay[PLAY_AREA_HEIGHT][PLAY_AREA_WIDTH];
void wipePlayArea()
{
for (int heightIdx = 0; heightIdx < PLAY_AREA_HEIGHT; ++heightIdx)
{
for (int widthIdx = 0; widthIdx < PLAY_AREA_WIDTH; ++widthIdx)
{
playAreaDisplay[heightIdx][widthIdx] = EMPTY_PLAY_SQUARE;
}
}
}
Hello sorry for the stupid question but I am very beginner in c++. I cannot describe the problem well because of my bad English. I'll add my code here that i have tried so far.
vector< vector<string> >allData;
int main(){
vector<string>test;
for(int i = 0; i<allData.size(); i++){
test = allData[i];
}
int id;
cout<<"enter Id"<<endl;
cin>>id;
if (id == test[2]){
string desc;
cout<<"enter ur description"<<endl;
cin>>description;
allData.push_back(description);
} else {
cout<<"there is no data with the id u have entered"<<endl;
}
}
Above code is just an example code. Lets say that there are 2 vectors inside the vector named allData, so when i enter the ID of a first vector i can add description into the vector which i have chosen by choosing it by its Id. Somehow i cannot do that thing like choosing the first or second vector by inputing their ids then add more datas into chosen 1. So please someone tell me what should i do. I know that above code is incomplete and awful but as i said before i am very beginner in c++
You can add values into nested vector just like a normal vector. So you could do allData[i].push_back(description) or even allData[i][j] = description to overwrite an existing value. However you are trying to push a string into allData which does not contain strings but rather Vectors of strings.
Additionally your first for loop runs through allData and saves each to test, overwriting test each time. When the loop is done test will simply contain the last element of allData. Thus your for loop is the equivalent of doing test = allData.back()
Well, if you need to access your child vectors directly, you need to declare your vector saying how many child vectors it has (without this, you have segmentation fault when trying to access it ie. allData[0] will be unitialised).
Let's say you have 2, so they will be allData[0] and allData[1], just like a normal array.
std::vector<std::vector<std::string>> allData (2);
allData[0].push_back("string0a");
allData[0].push_back("string0b");
allData[1].push_back("string1");
for(auto & a : allData[0])
std::cout << a << "\n";
Of course, you can add vectors dinamically too.
std::vector<std::vector<std::string>> allData;
std::vector<std::string> child0;
child0.push_back("string0");
allData.push_back(child0);
And to check if the id the user input is valid, you can do
if(id >= 0 && id < allData.size()) {
....
Your variable all_data is a vector of vectors representing rows and columns. You can create a scratch vector for a row, push_back() data on that scratch vector, then push_back() that scratch vector onto all_data like so:
#include <vector>
int main() {
std::vector<std::vector<int>> all_data;
for (int ii = 0; ii < 10; ii++) {
std::vector<int> row_data;
for (int jj = 0; jj < 10; jj++) {
row_data.push_back(ii * jj);
}
all_data.push_back(row_data);
}
return (0);
}
I want to write a program that randomly generates a tournament tree using only the number of challengers. I read into another such problem, but the answer described how ranks would take part and seeding the players, which went a little over head.
The problem I am facing is that my algorithm produces an infinite loop for values between 1 and 4 inclusively. For all values otherwise, the program runs as desired.
My approach was to take in an array of strings for the competitors' names. Then, I would iterate over each position and randomly select a competitor's name to take that spot. Because I am swapping the names, I have to check for duplicates in the array. I believe this is where my code is experiencing issues.
Here is the snippet that actually determines the tree
for(int i = 0; i < no_players;) {
int index = rand() % ((no_players - i) + i);
// randomly choose an element from the remainder
string temp = players[index];
bool unique = true;
// check all the elements before the current position
for(int j = 0; j < i; j++) {
// if the element is already there, it is not unique
if(players[j] == temp)
unique = false;
}
// only if the element is unique, perform the swap
if(unique) {
players[index] = players[i];
players[i] = temp;
i++;
}
}
Any help is much appreciated!
I've tried looking around but I can't find anything about this anywhere.
I'm writing a custom array class with a "push" function to add a value to the array.
It seems to work perfectly fine but won't execute more than once.
Take the main method below for example:
int main()
{
Array<int> test(4,5);
test.push(4);
test.writeOrdered("Output.txt");
return 0;
}
This will put the int value 4 into the array at the first available position and execute the writeOrdered function.
The following main method, on the other hand:
int main()
{
Array<int> test(4,5);
test.push(4);
test.push(5);
test.writeOrdered("Output.txt");
return 0;
}
This will put the number 4 into the array at the first available point as above and then stop. It won't execute any further lines of code.
Here's the push function for reference:
void push(Datatype p_item)
{
bool inserted = false;
int i = 0;
while (inserted == false)
{
if (m_array[i] < 0)
{
m_array[i] = p_item;
i++;
inserted = true;
cout << p_item << " saved to array" << endl;
system("pause");
}
}
}
You have an infinite loop. After the first insert m_array[0] >= 0 and i never grows. You would have found it out, had you debugged the code somehow.
Basically I don't understand your push function but the way it is, after you insert a non-negative value into the first position any further call to your push function results in a tight loop.
I imagine that you want the i++ outside the if statement.
Without seeing the full implementation of the Array class I would guess that the array m_array contains negative numbers by default. This will allow the first call to the push method to succeed. The next call to the method contains a value of 4 at index 0 and will be stuck in an infinite loop because inserted will never be set to true nor will the value of i be incremented.
I am having a hard time with two functions. Here are the project instructions:
Assignment:
Write a program which keeps track of the number of roaches in two adjacent houses for a number of weeks. The count of the roaches in the houses will be determined by the following:
The initial count of roaches for each house is a random number between 10 and 100.
Each week, the number of roaches increases by 30%.
The two houses share a wall, through which the roaches may migrate from one to the other. In a given week, if one house has more roaches than the other, roaches from the house with the higher population migrate to the house with the lower population. Specifically, 30% of the difference (rounded down) in population migrates.
Every four weeks, one of the houses is visited by an exterminator, resulting in a 90% reduction (rounded down) in the number of roaches in that house.
Here's my code:
#include <iostream>
#include <cmath>
using namespace std;
int house, increase, roaches, moreRoaches, fewerRoaches, filthyBeasts, change; // My variables for my four functions
int initialCount(int house);
int weeklyIncrease(int increase);
double roachesMigration(int moreRoaches, int fewerRoaches, int change);
int exterminationTime (int filthyBeasts);
// My four function prototypes
int main()
{
int houseA, houseB;
houseA = initialCount(houseA); //Initializing the initial count of House A.
houseB = initialCount(houseB); //Initializing the initial count of House B.
int week = 0;
for (week = 0; week < 11; week++) // My for loop iterating up to 11 weeks.
{
houseA = weeklyIncrease(houseA);
houseB = weeklyIncrease(houseB);
cout << "For week " << week << ", the total number of roaches in House A is " << houseA << endl;
cout << "For week " << week << ", the total number of roaches in House B is " << houseB << endl;
if((houseA > houseB)) // Migration option 1
{
roachesMigration(moreRoaches, fewerRoaches, change);
}
else if((houseB > houseA)) // Migration option 2
{
roachesMigration(moreRoaches, fewerRoaches, change);
}
if ((week + 1) % 4 == 0) // It's extermination time!
{
if ((rand() % 2) == 0) // Get a random number between 0 and 1.
{
houseB = exterminationTime(houseB);
}
else
{
houseA = exterminationTime(houseA);
}
}
}
return 0;
}
int initialCount(int house) // Initializing both houses to random numbers between 10 and 100.
{
int num;
num = (rand() % 91) + 10;
return num;
}
int weeklyIncrease(int increaseHouses) // Increasing the roaches in both houses by 30% weekly.
{
int increase = 0;
increase = (increaseHouses * .3) + increaseHouses;
return increase;
}
double roachesMigration(int moreRoaches, int fewerRoaches, int change)
{
more -= change;
fewer += change;
change = ((more - fewer) * .3);
return change;
}
int exterminationTime(int filthyBeasts) // Getting rid of the filthy little beasts!
{
filthyBeasts = (filthyBeasts * .1);
return filthyBeasts;
}
The issues are with the migration and extermination functions. My code runs fine, but at weeks 4 and 8, the randomly selected house should get exterminated, and the number of roaches in that house should be 90% less than the previous week. What do you guys think I should do to correct these issues? I really need all the help I can get!
Regarding this line:
roachesMigration(change);
change is not declared in your main function, hence the error. Also, roachesMigration function expects 3 parameters and not 1.
The variable change is not a global variable, but appears inside main (so it has no meaning inside main).
Your roachesMigration fonction is declared with three formal arguments (without default values), but you use it with one actual argument.
Ask your compiler to give you all the warnings and to produce debugging information (g++ -Wall -g on Linux). Improve the code till you get no warnings.
Learn to use a debugger (e.g. gdb on Linux).
Have fun.
Depending on the instructor, you will get zero marks for this code, even if you can get it to work perfectly! This is because you have not used any object orientated design in building your code. In C++, that means classes.
What sort of object do you need for this problem. A house!
What sort of attribute should your house have? Roaches!
So something like this:
class cHouse
{
int MyRoachCount;
...
};
If you start fresh, like this, you will find things start to fall neatly into place.
One possible way to handle the migration is like this pseudocode:
// compute size of migration
count = migration(houseA, houseB)
if (houseA < houseB)
add count to houseA
subtract count from houseB
else
add count to houseB
subtract count from houseA