int removeContact(Contact *newPtr, int runningTotal)
{
//define variables
string remove;
int next;
//prompt user for name they wish to remove
cout << "Enter the name you would like to delete (Last name first): ";
cin.ignore();
getline(cin, remove);
for (int t=0; t<=runningTotal; t++)
{
if (remove.compare(newPtr[t].name) == 0)
{
//calls function moveArrayElements function
moveArrayElements(newPtr, runningTotal, t);
//decrement runningTotal
runningTotal--;
//prompt user contact was found
cout << "Contact was found and deleted!";
next=1;
}
}
if(next!=1)
{
cout<< "ERROR: Contact was not found!";
}
return runningTotal;
}
This function is apart of a larger c++ program that is designed to manage a persons contact information. This function is suppose to remove a contact.
The problem I'm have is with the if (remove.compare(newPtr[t].name) == 0) statement. When my program gets to this part of the code it will crash without giving any errors. I tried straight up comparing both the stings with == operator, but this still results in a crash of my program...
Also, what make this so strange is that this code works perfectly when the function is called while my program is running with the contact that I'm trying to remove not stored in a text file.
However, when I close my program, and load my contact information from the text file, my program will crash... I know that my program is reading the file into the proper string array because I have a print function, so I know that all of my contacts are being transferred into the proper structure arrays...
Any ideas on how I can fix this? Any help would be appreciated! Thanks
UPDATE: I took the suggestions in the comments and changed my for loop to
t<runningTotal;
However, when I do this my program doesn't crash, but it wont's compare the strings...
If runningTotal is the size of your array, then the range of valid elements is [0, runningTotal). In the below code, you're looping up to runningTotal inclusive, when there isn't a valid Contact object there:
for (int t=0; t<=runningTotal; t++)
{
if (remove.compare(newPtr[t].name) == 0)
Therefore when you go and dereference newPtr[t], for t = runningTotal and then try and get the name element, you'll be causing undefined behaviour and may cause a crash.
Try changing t<=runningTotal to t < runningTotal to see if the problem goes away.
Also, is there a reason why you're using arrays as opposed to an std::vector?
i guess the for statement should be:
for (int t=0; t<runningTotal; t++)
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This is a C++ program to search a number and also display its index position if found in an array.
Program works fine. I just wanted to ask why we used k=1 in if statement because if we don't use it, then program won't work. Please explain the significance of k=1 in 2nd for loop in if statement.
#include<iostream>
using namespace std;
int main(){
int n;
cout<<"Size of Array: ";
cin>>n;
int arr[n];
cout<<"Type Elements of Array: ";
for(int i=0; i<n; i++)
{
cin>>arr[i];
}
int k;
cout<<"Enter No to be found: ";
cin>>k;
for(int i=0; i<n; i++)
{
if(arr[i]==k)
{
k=1;
cout<<"No is found at index position: "<<i<<endl;;
break;
}
else
{
cout<<"No is not found";
break;
}
}
return 0;
}
Looks like you are trying to do a linear search, there are some points I would like to clarify..
Never use int arr[n] using cin by user, it may work in yours, but not all compilers support it. Always allocate memory to the array statically like arr[10] or arr[20]
You are changing k which is the number that is to be found, I cannot understand why are you changing k . This is the number that is to be searched, you are mistakenly interpreting k as a flag variable, but it is NOT. Never try to change the input variable from the user.
Your program will only work, if the number you are searching is at 0th index, because, after that you are literally breaking from the loop in both if as well as else condition.
Here is a link to a better linear search code in c++, I hope it will clear your concepts C++ Linear Search
The problem is not with the k=1 statement. It lies in your logic of the else block.
Consider this:
n = 5
arr = [12, 2, 3, 14, 5]
k = 3
So initially i in the for loop starts from 0
It checks for equality:
Is arr[i] == k ?
arr[0] == 3 ?
12 == 3?
This is false, so your program goes to the else block, where it prints that the number was not found and breaks from the for loop. So essentially you are not checking all numbers, just the first one.
PS: Try and find a working logic for this on your own, it will be a good exercise and improve your understanding if you are getting started with programming (Hint: There are multiple ways, either through a flag variable or using the loop variable, etc). When your program doesn't work as you wanted it to, perform a dry run like I did on top.
You should go for the dynamic allocation of the array. Secondly, there is a mess with your if-else block. It checks only the first number in the array and then proceeds to the else portion. Your program can work fine but you should make sure that it searches the complete array for the number to be searched. You can do it by just removing the else part:
for(int i=0;i<n;i++)
{
if(arr[i]==k)
{
cout<<"No is found at index position: "<<i<<endl;;
return 0;
}
}
cout<<"No is not found.";
return 0;
enter image description hereI am using the STL in c++ and inside a bucle the cout doesn't prints correctly a float.
my program ads values to a vector and then passes it to a function to see if the condition exist, actually it works perfectly but just the cout doesn't word, I already tried using printf() but it gave the same result.
note:please algo give me feedback on my question is the first time i do one and English is not my natal language
my code:
#include<bits/stdc++.h>
#include<vector>
using namespace std;
void isthereanumber(vector<float> array);
int main(){
string ans;vector<float> array;float number;
do{
fflush(stdin);
cout<<"insert a value for the vector: "<<endl;
cin>>number;
array.push_back(number);
fflush(stdin);
cout<<"would you like to keep adding values to the vector? "<<endl;
getline(cin,ans);
}while(ans.compare("yes")==0);
isthereanumber(array);
return 0;
}
void isthereanumber(vector<float> array){
float suma =0;
for(vector<float>::iterator i=array.begin();i!=array.end();i++){
for(vector<float>::iterator j=array.begin();j!=array.end();j++){
if(i!=j){
suma = suma+array[*j];
}
}
if(suma=array[*i]){
cout<<"there is a number that the addition of every number in the array except the number is equal to the number \n";fflush(stdin);
cout<<"the number is: "<<suma;/*here is the cout that doesnt works properly or perhabs is something else i don't know*/
return;
}
}
cout<<"there is not a number with such a condition: ";
return;
}
As stated by cleggus already there are some issues present. Those need to be adressed first. After that there's a logical error in that suma just keeps growing.
Given the input 5,5,10 once we test for 10 we would like suma to be set to 0 again for it to work but it will be something like 30 now instead.
That can be solved by moving suma inside the outer loop.
Working example for input 5,5,10: https://godbolt.org/z/gHT6jg
I think you may have a couple of issues...
In your for loops you are creating iterators to the vector, but rather than just dereferencing them to access the indexed element you are dereferencing them and then using that as an index to the same vector.
Also Your last if statement has an assignment = rather than a comparison ==.
I believe this is closer to what you are trying to achieve (sorry I haven't had time to compile and check):
for(vector<float>::iterator i=array.begin();i!=array.end();i++){
for(vector<float>::iterator j=array.begin();j!=array.end();j++){
if(i!=j){
suma = suma+*j;
}
}
if(suma==*i){
cout<<"there is a number that the addition of every number in the array except the number is equal to the number \n";fflush(stdin);
cout<<"the number is: "<<suma;/*here is the cout that doesnt works properly or perhabs is something else i don't know*/
return;
}
}
I've been having an issue with a game I've been making in my C++ game programming class for school. For some reason, after calling a function which I'm using to manage the inventory based stuff, the function seems to complete and work (I think this because I put in cout commands at the end of it and they printed correctly, also the function runs twice in a row, and they both run), my entire game crashes and doesn't reach the next line. I tried commenting out all the code in the function and it still crashed. I commented out the function calls and it worked, but I still can't tell what is wrong with it. I'll put the code for the function and the section were I make the calls:
string inventoryFunction(int h, string ab)
{
if(h == 1)
inventory.push_back(ab);
else
if(h == 2)
{
for(int i=0; i < inventory.size(); i++)
{
if(inventory[i] == ab)
inventory[i].erase();
}
}
else
if(h == 3)
{
cout << inventory[0];
for(int i=1; i < inventory.size(); i++)
cout << ", " << inventory[i];
}
}
The function call:
if(answer.find("village") != string::npos)
{
cout << endl;
cout << "While looking around your village,\nyou found a stone sword and a cracked wooden shield!" << endl;
inventoryFunction(1, "stone sword");
inventoryFunction(1, "cracked wooden shield");
cout << "Would you like to set off on your adventure now?" << endl;
cin >> answer2;
capitalizeLower(answer2);
Not sure there's anything there likely to cause a crash, my advice would be to single-step your code in the debugger to see where it's falling over. It's quite possible the bug is somewhere totally different and it's just being exacerbated by the function calls modifying the vector.
That's the nature of bugs unfortunately, you can never really tell where they're actually coming from without looking closely :-)
However, there are a couple of issues with the code that I'd like to point out.
First, with regard to:
inventory[i].erase();
That doesn't do what you think it does. inventory[i] is the string inside your vector so it's simply erasing the string contents.
If you want to remove the string from the vector, you need something like:
inventory.erase (inventory.begin() + i);
Second, I'd tend to have three separate functions for addToInventory, removeFromInventory and listInventory.
It seems a little ... unintuitive ... to have to remember the magic values for h to achieve what you want to do, and there's no real commonality in the three use cases other than access to the inventory vector (and that's not really reason enough to combine them into the same member function).
On top of that, your function appears to be returning a string but you have no actual return statements and, in fact, none of the three use cases of your function require anything to be passed back.
The signature is better off as:
void inventoryFunction(int h, string ab)
In terms of the second and third points above, I'd probably start with something like:
void addToInventory (string item) {
inventory.push_back(ab);
}
void removeFromInventory (string item) {
for (int i = 0; i < inventory.size(); i++) {
if (inventory[i] == ab) {
inventory.erase (inventory.begin() + i);
break;
}
}
void listInventory () {
cout << inventory[0];
for (int i = 1; i < inventory.size(); i++)
cout << ", " << inventory[i];
}
You may also want to look into using iterators exclusively for the second and third functions rather than manually iterating over the collection with i.
It'll save you some code and be more "C++ic", a C++ version of the "Pythonic" concept, a meme that I hope will catch on and make me famous :-)
So by changing the inventoryFunction to a void function like #Retired Ninja said, the crash has stopped occurring and now the program is working great.
Also, #paxdiablo pointed out that I was using the inventory[i].erase() thing incorrectly, so thanks a bunch to him, because now I won't have to come back on here later to try to fix that :D
string inventoryFunction(int h, string ab)
should return a string but does not have any return statements. Of course it works, after you change it to a void function, which correctly does not return anything. Interesting is, that you are able co compile this code without an error - normally a compiler would show you this problem.
Today I tried to program the Sieve of Eratosthenes and it works as far as it provides me with the prime numbers. But I have a problem with the dynamic array I don't understand.
First problem: As soon as I try to enter a "big" value for n (for example 120), the program crashes, it doesn't even allocate the memory.
Second problem: If I enter a value like 50 it is able to give out the correct prime numbers but crashes before it deletes the array.
Third problem: If I enter a very small value like 5 it is able to execute the entire program, it gives out the correct numbers and deletes the memory.
But I don't understand why it acts so differently. 120 boolean values can't crash my memory, at least I think so. And why isn't it able to delete an array of 50 values but is actually able to delete an array of 5 values?
Can anyone tell me what's the problem?
int n;
cin >> n;
n=n+1;
bool *feld = new bool[n];
for(int i=2;i<n;i++)
{
int j=i*i;
feld[j]=true;
for(;j<n;j+=i)
feld[j]=true;
}
for(int i=2;i<n;i++)
if(!feld[i])
cout << i << endl;
else;
delete[] feld;
feld = NULL;
Your problem is here:
int j=i*i;
feld[j]=true;
there is no check as to whether j < n so you are stomping over unallocated memory when j >= n.
This code is wrong
bool *feld = new bool[n];
for(int i=2;i<n;i++)
{
int j=i*i;
feld[j]=true;
...
}
Suppose n == 10 and i == 9, then j == 81 but you only have 10 elements in your bool array.
This is how it works when you write bugged programs, sometimes it seems to work, it might even give the right answer, other times it will crash. This is a very important lesson, and you're actually lucky to have learned it early.
Actually It's not just that feld[j]=true; is causing the error.
Also, you don't need that line at all before the loop.
because, it's the first case inside the loop.
The codes in my main program are given below; here I read a file called test.dat and data of this file put in to my structure so for that I used a class called MyData (my_data.hpp).
int main()
{
// cout<<"this my program"<<endl; // when this delete, this codes are not working
bool ok=true;
MyData my_data("test.dat", ok);
if(ok==false){
cout<<"Error, unable to read file1.";
return 0;
}
ACalculation a_calculation(&my_data);
For the calculation part, I used another class, AClaculation (a_calculation.hpp). Here I used pointers to speedup my program.
ACalculation (MyData * my_data){
MYData::iterator i;
for (i= my_data ->begin(); i!= my_data ->end(); i++){
if(i->A() > max){
max = i->A();
}
}
cout<<”my max value is:”<<max;
My program does not show any errors but when I run it, it does not show the result of my max value. But when I added a “cout” code at the beginning of the main program then it shows the result. It means, when I delete this line:
cout<<""this my program";
the program does not show correct output. But when I add it again, it workq. I can't understand where the error of my program is?.
Please help me to find out my mistakes here.. thanks
I think you have to flush the console printing an endl