I am sorry i'm new learner in programming. I would like to ask for help where i want to display a range number start from 200 until 400 but it should not display number 250 in it.
This is what i have done.
int main () {
for (int i=200; i<=400; i++) {
std::cout << "value of i: " << i << endl;
}
return 0;
}
I was sucessfuly display the range number, but it display all number.
If you want to avoid the if for every iteration, you could of course also split it into two loops:
for (int i = 200; i < 250; ++i)
std::cout << "value of i: " << i << endl;
for (int i = 251; i <= 400; ++i)
std::cout << "value of i: " << i << endl;
Pretty simple, but simple can be very good in this business.
If 250 is the only number you don't want to display in your range, you need to use and if statement. This statement would be stating that you should print number only if they are different from 250.
for (int i=200; i<=400; i++) {
if (i != 250) { // if my current number i is different from 250 I print it
std::cout << "value of i: " << i << std::endl;
}
}
Related
I am struggling with printing an array with 4 rows and 4 columns, when I initialized the array and entered all the values. Then, I used for loop to get all the values together so I can print them. But I get is an array that companied all the values in one row.
I have attached the output when I run the code.
Here is a portion of my code, it is long code but I am struggling in specific part:
#include <iostream>
using namespace std;
int main()
{
cout << "The martix before I flipped it: " << endl;
cout << endl;
int array[4][4] = { 16,3,2,13,5,10,11,8,9,6,7,12,4,5,14,1 };
for (int i = 0; i < 4; i++) {
for (int j = 0; j < 4; j++) {
cout << array[i][j] << " ";
}
}
return 0;
The standard output utility std::cout is a stream from the stl and, as such, its << operator does not usually automagically append a linebreak.
Which is quite practical since, otherwise, you would not be able to print multiple numbers on a single line.
That being, said, you'll need to add the linebreak manually, like so :
for (int i = 0; i < 4; i++) {
for (int j = 0; j < 4; j++) {
std::cout << array[i][j] << " ";
}
std::cout << std::endl;
}
Alternatively, you can consider printing lines 4 at a time since your matrix is of constant size :
for (int i = 0; i < 4; i++) {
std::cout << array[i][0] << " "
<< array[i][1] << " "
<< array[i][2] << " "
<< array[i][3] << " " << std::endl;
}
Have a great day,
I'm solving the Traveling Salesman Problem via an ACO implementation in C++. However, I found out that the program I've built so far gives a segmentation fault.
(Note: I've limited the algorithm to only do one iteration of the colony for debugging purposes).
First off, I have a total of 52 cities taken from a file, and I distribute the ants so that every city has the same number of ants starting from it.
To store the distances between every pair of cities, I'm using a vector of vectors of doubles called Map (a square matrix). However, half-way during the execution it looks like these vectors are deleted. In this instance, it happens when calculating the path for the ant number 55. I've added a section of code just to highlight exactly where it crashes:
//DEBUGGING SECTION
cout << "Size Roulette: " << Roulette.size() << endl;
cout << "Size Remain: " << RemainingCities.size() << endl;
cout << "Size Map: " << Map.size() << " x " << Map[0].size() << endl;
int k = 0;
cout << "Test: Map access: " << endl;
for(int i = 0; i < Map.size(); ++i) // HERE IT CRASHES AT ANT NUMBER 55
cout << Map[0][i] << " ";
cout << endl;
cout << "Test: Operation: " << Map[Colony[ant_i][city_i-1]][RemainingCities[k]] << endl;
Roulette[k] = pow((MAX_DIST - Map[Colony[ant_i][city_i-1]][RemainingCities[k]]), heur_coef) + pow((pheromones[Colony[ant_i][city_i-1]][RemainingCities[k]]), pher_coef);
//END OF DEBUGGING SECTION
There, the function Map[0].size() normally returns 52 (just like Map.size(), as it's supposed to be a square matrix), but at the crashing iteration it returns what looks like a memory address, and the moment I try to access any element, a segmentation fault occurs.
I have checked that the memory access is always correct, and I can access any other variable without issue except Map until that 55th ant.
I've tried different seeds for the roulette method, but it always crashes at the same place.
I have also varied the number of ants of the colony. If it's just one ant per city, the program executes without issue, but for any higher amount the program always crashes at the 55th ant.
You can download the full cpp file and the reading .tsp file from github:
https://github.com/yitosmash/ACO
In any case, I'll leave the full function here:
void ACO(const vector<City>& cities, const vector<vector<double>>& Map, int max_it, int num_ants, double decay, double heur_coef, double pher_coef, double pher_coef_elit)
{
srand(30);
//Initialise colony of ants (each ant is a vector of city indices)
vector<vector<int>> Colony(num_ants, vector<int>(cities.size(), 0));
//Initialise pheromone matrix
vector<vector<double>> pheromones(cities.size(), vector<double>(cities.size(), 0));
//Initialise costs vector(for etilist expansion)
vector<double> costs(cities.size(), 0);
//Auxiliar vector of indices
vector<int> cityIndices(cities.size());
for (int i = 0; i < cities.size(); ++i)
cityIndices[i] = i;
//Longest distance from Map, used for heuristic values.
vector<double> longests(cities.size(), 0);
for(int i = 0; i < cities.size(); ++i)
longests[i] = *(max_element(Map[i].begin(), Map[i].end()));
const double MAX_DIST = *(max_element(longests.begin(), longests.end()));
longests.clear();
int i=0;
while(i<max_it)
{
for(int ant_i = 0; ant_i < num_ants; ++ant_i)
{
cout << "Ant: " << ant_i << endl;
//City for ant_i to start at; each ant is assigned a determined starting city
int starting_city = (int) ((float)ant_i/num_ants*cities.size());
//cout << starting_city << endl;
Colony[ant_i][0] = starting_city;
//Get a vector with the cities left to visit
vector<int> RemainingCities = cityIndices;
//Remove starting city from remaining cities
RemainingCities.erase(RemainingCities.begin() + starting_city);
//Create path for ant_i
for(int city_i = 1; city_i < Colony[ant_i].size(); ++city_i)
{
cout << "Calculating city number: " << city_i << endl;
//Create roulette for next city selection
vector<double> Roulette(RemainingCities.size(), 0);
double total = 0;
//DEBUGGING SECTION
cout << "Size Roulette: " << Roulette.size() << endl;
cout << "Size Remain: " << RemainingCities.size() << endl;
cout << "Size Map: " << Map.size() << " x " << Map[0].size() << endl;
int k = 0;
cout << "Test: Map access: " << endl;
for(int i = 0; i < Map.size(); ++i) // HERE IT CRASHES AT ANT NUMBER 55
cout << Map[0][i] << " ";
cout << endl;
cout << "Test: Operation: " << Map[Colony[ant_i][city_i-1]][RemainingCities[k]] << endl;
Roulette[k] = pow((MAX_DIST - Map[Colony[ant_i][city_i-1]][RemainingCities[k]]), heur_coef) + pow((pheromones[Colony[ant_i][city_i-1]][RemainingCities[k]]), pher_coef);
//END OF DEBUGGING SECTION
for(int j = 0; j < RemainingCities.size(); ++j)
{
//Heuristic value is MAX_DIST - current edge.
Roulette[j] = pow((MAX_DIST - Map[Colony[ant_i][city_i-1]][RemainingCities[j]]), heur_coef) + pow((pheromones[Colony[ant_i][city_i-1]][RemainingCities[j]]), pher_coef);
total += Roulette[j];
}
cout << endl;
//Transform roulette into stacked probabilities
Roulette[0] = Roulette[0]/total;
for(int j = 1; j < Roulette.size(); ++j)
Roulette[j] = Roulette[j-1] + Roulette[j] / total;
//Select a city from Roulette
int chosen = 0;
double r = (double) rand()/RAND_MAX;
while(Roulette[chosen] < r)
chosen++;
//Add chosen city to
Colony[ant_i][city_i] = RemainingCities[chosen];
RemainingCities.erase(RemainingCities.begin() + chosen);
}
cout << endl;
//Save cost of ant_i, for elitist expansion
costs[ant_i] = pathCost(Colony[ant_i], Map);
}
i++;
}
}
That part is very suspicious :
for(int i = 0; i < Map.size(); ++i) // HERE IT CRASHES AT ANT NUMBER 55
cout << Map[0][i] << " ";
because i is the size of the map but you use it as an index in a probable string / vector, so you probably go out of the string/vector with an undefined behavior
probably you want
for(int i = 0; i < Map.size(); ++i)
cout << Map[i] << " ";
or
for(int i = 0; i < Map[0].size(); ++i)
cout << Map[0][i] << " ";
As I said in a remark at a moment RemainingCities[0] values -163172699 first in
cout << "Test: Operation: " << Map.at(Colony.at(ant_i).at(city_i-1)).at(RemainingCities.at(k)) << endl;
so is not a valid index in Map, but there is visible reason to have that looking at the code, so the reason is a probable write out of a vector destructing your memory elements.
To detect where I replaced all the [...] by .at(...) and the first error I have is in ACO at the line
costs.at(ant_i) = pathCost(Colony.at(ant_i), Map);
where ant_i values 52 while costs has 52 entries and Colony 260, so the error concerns costs
note that ant_i is set by the loop
for(int ant_i = 0; ant_i < num_ants; ++ant_i)
and in that case num_ants value 260 so much more than the size of costs which is defined as
vector<double> costs(cities.size(), 0);
but cost is just allocated and set but never read, so its goal is just to destruct the memory.
If I remove the two lines concerning it I do not have anymore an error and the program ends normally, there is no exception in a .at(...) and valgrind detect no error too.
code:
#include <iostream>
#include <vector>
int main () {
std::cout << "Please, enter the number of iterations: "; //Inputs
int iterations;
std::cin >> iterations;
std::cout << "Which term would you like to know: ";
int term;
std::cin >> term; //End inputs
std::vector<int> series; //definition of vector "series"
for (int n = 1; n <= iterations; n++) { //creation of "series"
int next = (2 * n - 3);
series.push_back(next);
}
std::cout << "The value of term " //prints the n term
<< term
<< " is: "
<< series[term-1] //term-1 "adjust" the indexing
<< std::endl;
std::cout << "The entire serie up to "
<< iterations
<< " terms is: ";
for (int i = 0; i < series.size(); i++) { //prints (elements of vector) "series"
std::cout << series[i] << ' ';
if (i == series.size()-1) { //new line only at the end the series
std::cout << std::endl;
}
}
return 0;
}
I got 9/10 with this comment: "if condition inside loop will only be satisfied once, but checked every time. Move outside of loop".
I really don't how could I place the if statement out of the loop.
The scope of that for-if statement is to add a new line only at the end of the vector "series".
I can't think about anything else but for sure I'm experienced enough and there is another more elegant solution.
I'm asking here because I have to submit another assignment and I don't want to submit it with the same error.
PS: the other comment was: light over-commenting. Did I really commented to much?
You print the endl at the end of the for loop, so you can to add the line of endl when you go out from the loop and remove the line at the for loop, it will give you the same result
The code:
for (int n = 1; n <= iterations; n++) { //creation of "series"
int next = (2 * n - 3);
series.push_back(next);
}
std::cout << "The value of term " //prints the n term
<< term
<< " is: "
<< series[term-1] //term-1 "adjust" the indexing
<< std::endl;
std::cout << "The entire serie up to "
<< iterations
<< " terms is: ";
for (int i = 0; i < series.size(); i++) { //prints (elements of vector) "series"
std::cout << series[i] << ' ';
}
std::cout << std::endl;
return 0;
}
What you are trying to do is to print a newline after the last element. Here, you are checking for each element if it is the last. However, you don't need to do that.
Another way to do "After the last element" is "after all elements", so after the loop. Just process all the elements with the for loop, then print the newline.
I'm not giving the code, since it is an assignment, but this should be clear enough.
As for commenting: don't document the obvious. Of course, for different levels, obvious is something different. But for the declaration of the "series" vector, the comment doesn't add anything to the code, for instance.
I need the user input to be saved into my array and then output the array before the user inputs the next time. I have been moving things around different ways but cannot seem to get them to perform properly. I tried to cut down the code to the two functions I am having issues with.
void PlayGame()
{
const int HighestNum = 50;
const int LowestNum = 1;
int RandomNumber = LowestNum + rand() % HighestNum; //set for better random results
cout << "Guess the random number between " << LowestNum << " and " << HighestNum << "!\n\n";
const int attempts = 15;// limits the attempts to guess the random number to 15
int Guess [attempts] = {};
cout << "Enter your guess " << endl;
for (int count = 0; count < attempts; count++)
{
cin >> Guess[count];
int z = RandomNumber, y = Guess[count], r;
r = reviewGuess (z,y);//calling the function that determines the results
switch (r)//switch statement for function results, letting the user know if they matched the number, if the number is higher, or lower
{
case 0:
cout << "You Win!!" << endl;
cout << "\n";
cin.get();
return;
case 1:
cout << "The number is higher than your guess" << endl;
break;
case -1:
cout << "The number is lower than your guess" <<endl;
break;
}
if (count == 15)
{
cout << "Sorry, no guesses remain. The random number was... " << RandomNumber << "!";//so the user can see the random number at the end of their attempts
cout << "\n";
cin.get();
Again();
}
}
return;
}
int DisplayGuess(int member[])
{
for(int i = 0; i < 15; ++i)
cout << "\nGuess " << i + 1 << ": " << member[i];
cout << endl;
return;
}
Try this inside your loop
if(count > 0)
{
for (int j= 0; j < count; j++)
{
cout<<Guess[j];
}
}
Call DisplayGuess() in the first line of the for loop. Since the first you time you call it your array is empty, it shouldn't output anything.
So,
for (int count = 0; count < attempts; count++)
{
DisplayGuess(Guess[count]);
cin >> Guess[count];
int z = RandomNumber, y = Guess[count], r;
r = reviewGuess (z,y);//calling the function that determines the
results
. . . . . .
I am making a 20 questions game in C++ and have everything working, except for the displayWords function. The code I currently have keeps breaking. Any explanation would be appreciated! Thank you!
void displayWords()
{
int x = 0;
string words[50] = {"LCHS","Shark","Pencil","Pizza","New York","Fish","Car","Ice Cream","Los Angeles","Bird","Basketball","Fried Chicken",
"Dog","Tiger","Penguin","Plane","Rock","Barbecue Sauce","Mustard","Ketchup","Hot sauce","Peppers","Salt","Tacos","Shrimp","Pickels",
"Tomatos","Bannanas","Burger","Computer","Iphone","Motorcycle","Bicycle","Skateboard","Lightbulb","Golf Ball","Surfboard","Luggage",
"Rollercoaster","Cat","Lion","Cockroach","Grasshopper","Beach","Theme Park","Swimming Pool","Bowling Ally","Movie Theater","Golf Course","Shopping Mall"};
cout << "The following list of words are what the computer is capable of guessing" << endl;
cout << endl;
while(x < 50)
{
for (int y = 0; y <= 5; y++)
{
cout << words[x] << ", ";
if(x<50)
x++;
}
cout << endl;
}
}
I would like it to display the list of 50 words in an organized fashion.
By example, as:
for( int x = 0; x<sizeof(words)/sizeof(*words); x++ ) {
if( x%5==0 ) cout << endl; else cout << ", ";
cout << words[x];
}
take into account the problematic of the array's size calculation: see this link How do I find the length of an array?
If I understand correctly, you want your list displayed as 5 columns. Simplest way, use a nested for loop and proper formatting with std::setw (must #include <iomanip>):
for(size_t i = 0; i < 10; ++i)
{
for(size_t j = 0; j < 5; ++j)
{
std::cout << std::setw(20) << std::left << words[i * 5 + j];
}
std::cout << std::endl;
}
Your actual loop is incorrect, as it will lead to repetitions.
Maybe I'm not interpreting your question correctly but if you want to just print out the 50 words then you can use something like the code below. Not sure of the reason that the nested for loop iterating y was there.
Edit
void displayWords()
{
int x;
string words[50] = {"LCHS","Shark","Pencil","Pizza","New York","Fish","Car","Ice Cream","Los Angeles","Bird","Basketball","Fried Chicken",
"Dog","Tiger","Penguin","Plane","Rock","Barbecue Sauce","Mustard","Ketchup","Hot sauce","Peppers","Salt","Tacos","Shrimp","Pickels",
"Tomatos","Bannanas","Burger","Computer","Iphone","Motorcycle","Bicycle","Skateboard","Lightbulb","Golf Ball","Surfboard","Luggage",
"Rollercoaster","Cat","Lion","Cockroach","Grasshopper","Beach","Theme Park","Swimming Pool","Bowling Ally","Movie Theater","Golf Course","Shopping Mall"};
cout << "The following list of words are what the computer is capable of guessing" << endl;
cout << endl;
for(x = 0; x < words.size();x++)
{
cout << words[x]<< ", ";
}
}
Also some information on how the code is breaking, like are any errors being thrown or has debugging caused issues so far?