I have a question regarding a school lab assignment and I was hoping someone could clarify this a little for me. I'm not looking for an answer, just an approach. I've been unable to fully understand the books explanations.
Question: In a program, write a function that accepts three arguments: an array, the size of the array, and a number n.
Assume that the array contains integers. The function should display
all of the numbers in the array that are greater than the number n .
This is what I have right now:
/*
Programmer: Reilly Parker
Program Name: Lab14_LargerThanN.cpp
Date: 10/28/2016
Description: Displays values of a static array that are greater than a user inputted value.
Version: 1.0
*/
#include <iostream>
#include <iomanip>
#include <cmath>
using namespace std;
void arrayFunction(int[], int, int); // Prototype for arrayFunction. int[] = array, int = size, int = n
int main()
{
int n; // Initialize user inputted value "n"
cout << "Enter Value:" << endl;
cin >> n;
const int size = 20; // Constant array size of 20 integers.
int arrayNumbers[size] = {5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24}; // 20 assigned values for the array
arrayFunction(arrayNumbers, size, n); // Call function
return 0;
}
/* Description of code below:
The For statement scans each variable, if the array values are greater than the
variable "n" inputted by the user the output is only those values greater than "n."
*/
void arrayFunction(int arrayN[], int arrayS, int number) // Function Definiton
{
for (int i=0; i<arrayS; i++)
{
if (arrayN[i] > number)
{
cout << arrayN[i] << " ";
cout << endl;
}
}
}
For my whole answer I assume that this:
Question: In a program, write a function that accepts three arguments: an array, the size of the array, and a number n. Assume that the array contains integers. The function should display all of the numbers in the array that are greater than the number n .
is the whole assignment.
void arrayFunction(int[], int, int); is probably the only thing you could write. Note however that int[] is in fact int*.
As others pointed out don't bother with receiving input. Use something along this line: int numbers[] = {2,4,8,5,7,45,8,26,5,94,6,5,8};. It will create static array for you;
You have parameter int n but you never use it.
You are trying to send variable to the function arrayFunction but I can't see definition of this variable!
Use something called rubber duck debugging (google for it :) ). It will really help you.
If you have some more precise question, ask them.
As a side note: there are better ways of sending an array to the function, but your assignment forces you to use this old and not-so-good solution.
Would you use an if else statement? I've edited my original post with the updated code.
You have updated question, then I update my answer.
First and foremost of all: do indent your code properly!!!
If you do that, your code will be much cleaner, much more readable, and it will be much easier understandable not only for us, but primairly for you.
Next thing: do not omit braces even if they are not required in some context. Even experienced programmers only rarely omit them, so as a beginner you should never do so (as for example with your for loop).
Regarding if-else statement the short answer is: it depends.
Sometimes I would use if (note: in your case else is useless). But other times I would use ternary operator: condition ? value_if_true : value_if_false; or even a lambda expression.
In this case you should probably settle for an if, as it will be easier and more intuitive for you.
Aside from the C++ aspect, think about the steps you need to do to figure out if a number is greater than a certain value. Then do that for all the numbers in the array, and print out the number if it's greater than n. Since you have a 'for' loop, it looks like you already know how to do a loop and compare numbers in C++.
Also, it looks like in your arrayFunction you are trying to input values? You can't input a whole array's worth of values in a single statement like you appear to be trying (also, 'values' is not the name of any variable in arrayFunction, so that would not be recognized when you try to compile it).
Related
I'm playing with a function to get used to some C++ syntax.
Now I think, I might have misunderstood:
I'm writing to a static (?) array I had defined as myArray[0] for experimenting.
So it seems NOT to be static, but sizeof(myArray) always returns 0 (?)
but I can find mem address for each item (while I have no idea, how to get the number of items this way).
The other thing I don't understand, is why I can write myInt = myFloat?
So, what IS a static array? And should I better use <vector> for an array of undefined length?
(You could find the whole code here int2bin main.cpp)
#include <iostream>
//#include <regex>
int main()
{
while(true) {
//VARS
unsigned int arrBin[0], intNum; //working, if set [0]! NOT static???
unsigned int *pArr0 = &arrBin[0];
unsigned int *pArr1 = &arrBin[1];
std::cout << sizeof(arrBin) << '\n'; // 0 => sizeof() here items and not mem space?
std::cout << pArr0 << '\n';// 0x7fff12de6c38
std::cout << pArr1 << '\n';// 0x7fff12de6c3c
int i;
float refNum;
std::cout << "\n\nEnter a number to convert: ";
// GET INPUT
std::cin >> refNum; // float
intNum = refNum; // get int of the dec for comparing. Why does this "int = float" work???
unsigned int arrBin[0]
The size of an array variable must not be 0. The program is ill-formed. Don't do this.
unsigned int *pArr1 = &arrBin[1];
Here, you use subscript operator beyond the bounds of the array (beyond one past last element), so the behaviour of the program is undefined. Don't do this.
(while I have no idea, how to get the number of items this way).
The number of items is 0 (or would be if that was allowed in the first place).
The other thing I don't understand, is why I can write myInt = myFloat?
You haven't even declared such identifiers.
I'm writing to a static (?) array I had defined as myArray[0] for experimenting.
By 'static' you probably mean 'fixed-sized'. static means something totally different, see https://www.geeksforgeeks.org/static-keyword-cpp/.
So it seems NOT to be static
It is not static, hence, it's not surprising that it's not static.
but sizeof(myArray) always returns 0
Its size is 0, as the size of 0 was specified. While this is not supported by the standards, it's possible that some compilers allow it.
but I can find mem address for each item (while I have no idea, how to get the number of items this way).
&arr[i] yields the address.
The other thing I don't understand, is why I can write myInt = myFloat?
Integer numbers are always real numbers, but real numbers are not always integer numbers. So, how would you store 0.5 as an integer? You could cast it or you could round it.
So, what IS a static array?
In the link I have provided you, it is mentioned that static variables in a function are variables for whom memory is allocated for the whole duration of a program. Hence, a static array is an array declared with the static keyword for which space are allocated for the whole lifecycle of your program. No such array was declared in your function.
And should I better use for an array of undefined length?
This is opinionated. You could create a pointer and navigate to items using pointer arithmetics, achieving the same behavior as with arrays, but without the length being fixed and with a slightly different syntax. Or you could use a library, a vector or whatever fits your task and taste.
I have been given following assignment
Write a simple telephone directory program; contain two dimensional arrays in which you have hard code names and telephone number. Then declare a simple character array. You have to prompt user to enter any name, which you want to search. This name should be store in this character array, then search this name from the two dimensional array. If number is found against entered name then program should display the number against this name, and if not found then program should display the message that name is not registered.
Here is my code but i could not get the number when i search for the name. I am new to coding so i am having trouble making this code work. Help is appreciated.
#include <iostream>
#include <conio.h>
using namespace std;
int getPhone(int p[5][10],int row, int col, char key[10],char n[5][10]);
int main() {
int i,j;
char search[10];
const int r = 5;
const int c = 10;
int element;
int phone[r][c] =
{
42-5429874,
42-5333156,
42-9824617,
42-9927562,
42-6238175
};
char name[r][c] = {"shazia","zara","sana","ahmad","maha"};
cout<<"\nEnter name to find in directory : ";
cin>>search[r];
element = getPhone(phone,r,c,search,name);
cin.get();
return 0;
}
int getPhone(int p[5][10],int row,int col,char key[10], char n[5][10]) {
int i, j;
for(i=0;i<row;i++)
for(j=0;j<col;j++)
p[5][10] = p[i][j];
if(key[j] = n[5][10])
cout<<"The desired number is: "<<p[i][j]<<endl;
else if(key[j]!=n[5][10])
cout<<"Sorry! This name is not registered.";
return p[i][j];
}
Your code contains several mistakes. Let's examine them.
for(i=0;i<row;i++)
for(j=0;j<col;j++)
p[5][10] = p[i][j];
Here, you make no change on your array, because just the value of p[5][10] is changed. Furthermore, you access an invalid memory zone, because array indexes go from 0 to size - 1 in C++. So last index is p[4][9].
if(key[j] = n[5][10])
In C++, comparing two values needs two =, because only one is an affectation that results the if to be always true. A tip to remember: two values to compare need two =.
else if(key[j]!=n[5][10])
The same than before, you access invalid memory zone. And are you sure that j is valid, e.g less than 10 ? If not, you do double invalid access.
cin>>search[r];
As search is an array of char, you do an input of only a single char there, which I think is not what you want and that can leads to segfault.
int phone[r][c] =
{
42-5429874,
42-5333156,
42-9824617,
42-9927562,
42-6238175
};
Your array is not good, a simple 1-dimension array is enough, not 2-dimensions. Furthermore, 42-54.. does a subtraction, and I think is not what you want.
There are others mistakes. But why not using C++ abstractions, like std::vector, or std::string? Your life would get so much easier. But I guess you have an old teacher that never took time to learn C++ news, or that is not a good teacher.
As a beginner, I suggest you to read C++ Primer and Programming: Principles and Practice Using C++ to introduce you both programming and modern C++.
I'm in a basic csci, computer programming course, and have been fiddling with this code for hours. I'm trying to pass an array through a function, and my code will not compile. I can't figure out what's going wrong with my code. It is as follows:
int buildArray (double*);
int main ()
{
int valuesPerLine;
int randomValues;
double array[110];
srand(time(NULL));
cout<<"How many values should be displayed per line? ";
cin>>valuesPerLine;
randomValues=buildArray(array[]);
cout<<array[50];
return (0);
}
int buildArray (double array[])
{
int t; //t is the total number of numbers in the array
t=rand();
array[t];
for (int i=0; i<t; i++)
{
array[i]=randDouble();
}
return(t);
}
The cout<<array[50]; is just there for myself to see if the answer changed. It will not be in the final code.
Is there something simple I missed? I've usually been able to help other people with the code in class but for some reason I can't figure this one out.
Thanks for everything!
P.S.
This isn't the entire code, and I know in this case I haven't said what the randDouble is, but I don't believe that is important, because that code seems to compile fine as it is. If it is needed, let me know and I can post it below.
When passing an array to function, you only pass the pointer to the first element of the array.
In your case, it would be:
randomValues = buildArray(array);
My program is this:
#include<iostream>
#include<fstream>
using namespace std;
int main()
{
char choice;
int o,i,marks[i],ttlcredit=0;
double ttlGPA=0,finalGPA=0,credit[7][2],clsavg;
cout<<"Please enter what you want to calculate"<<endl;
cout<<"A for calculating Class Average GPA"<<endl;
cout<<"B for calculating a Specific GPA"<<endl;
cout<<"Your choice is? ";
cin>>choice;
cout<<endl;
if (choice == 'A'||choice == 'a')
{
cout<<"=========================================="<<endl;
cout<<" Class Average GPA"<<endl;
cout<<"=========================================="<<endl<<endl;
cout<<"Please enter the number of students in the class: ";
cin>>number;
for(i=0;i<number;i++)
{
cout<<"\nEnter student #"<<i+1<<"'s marks: ";
cin>>marks[i];
ttlGPA=ttlGPA+marks[i];
}
clsavg=ttlGPA/number;
cout<<"\nThe Average is: "<<clsavg<<endl;
}
else
{
}
}
It is half completed. When I build and run on CodeBlocks, an error instantly appeared:
I tried finding the source of error and I think that it is caused by the following in the code:
int o,i,marks[i],ttlcredit=0;
What makes me think so is because when I remove the [i] from marks[i], I will be not receive that error.
I think is stack overflow because I use Microsoft Visual Studio to help me debug and this is the error they gave me:
Unhandled exception at 0x0041419e in Project (1).exe: 0xC00000FD: Stack overflow.
My question is...
Is that the main cause of problem?
How do I resolve this issue?
You have to initialize the marks array with a positive length.
Get the number of students first, THEN create the array using that number.
Also, you need to declare the variable number.
As the other answers stated correctly, the problem is that int i is used uninitialized. However, the proposed fix
// initialze i
int marks[i];
is not standard C++, but only available through a compiler extension. In C++, the length of a built-in array must be a compile time constant. The better solution would be using std::vector:
// initialize i (better make it std::size_t instead of int)
std::vector<int> marks (i);
This will create a variable length array in a safe and standard conforming way.
First thing to say is that you simply shouldn't use arrays. They just are too weird in C and C++, and we have superior alternatives in modern C++.
Anyway, whether you use arrays or vectors, there are some important issues. Before discussing marks[i], it's simpler to look at credit[7][2] in this code.
int o,i,marks[i],ttlcredit=0;
double ttlGPA=0,finalGPA=0,credit[7][2],clsavg;
The dimensions are explicit in this declaration of credit. It's seven-times-two. Simple enough. You can read and write to credit[0][0] and credit[6][1] and many other values. But if you go outside the range, e.g. try to use credit[7][0], your program will compile and will probably appear correct for a while, but it could behave very badly and it is undefined how it will behave. It could decide to delete all the files on your computer, it is (seriously) entitled to do anything random and crazy. This is Undefined Behaviour.
Anyway, the really weird line is the declaration of marks.
int marks[i];
This definitely doesn't do what you think it does. It doesn't create an array that can be "indexed with arbitrary i". No, it allocates an array whose size is the initial value of i. But i is undefined at this stage so this is meaningless.
But i isn't relevant here anyway. How big do you want this array to be? The answer is number, isn't it? That is the number of people you'll store in your array.
So, a small improvement is to do this instead of int marks[i].
int marks[number];
But even this isn't correct. The value of number isn't set until the line cin >> number;, therefore you must declare int marks[number] after the line cin >> number; in order to ensure that marks has the correct size.
But, but, but, even after all this, we still don't have standard C++. It's OK to do int credit[7][2] because the size is fixed at compile time. You are normally not allowed to set the size of an array at runtime, e.g. int marks[number]. You might be able to use it if your compiler allows this extension (it's called Variable Length Array, from C).
So, this is not standard C++, and it's potentially very dangerous (see the Undefined Behaviour). What's the solution?
The solution is the standard solution for any problem involving arrays. Stop using arrays. (Really advanced programmers, in particular situations, might use std::array in modern C++, or even write their own clone of std:: array in older C++. But raw C [] arrays are to be avoided where possible.)
#include<vector>
int o,i,ttlcredit=0;
std::vector<int> marks;
marks is initially empty. We don't do cin >> marks[i];. Instead we use push_back to append new items to the end of the list.
int next_mark;
cin >> next_mark;
marks.push_back(next_mark);
Also, don't use marks[i] with a vector. It might look OK, but it is dangerous. Better to use marks.at(i) to read or write the element. at will do bounds checking for you, giving you a proper error message if i is too small (less then 0) or too big for the size of the vector.
int o,i,marks[i],ttlcredit=0;
i is not initialized. initialize i first.
If you are not sure of the size of the array, allocate it dynamically.
use new
refer this link on how to use new - cpluspluss
I am new to C++. Recently, I have been stuck with a simple code of C++ features. I will be very grateful if you can point out what exactly the problem. The code as follows:
// used to test function of fill
#include<iostream>
#include<algorithm>
using namespace std;
int main(){
int val = 0;
int myarray[8];
//fill(myarray,myarray+2,1);
for(;val < 8;++val){
cout << myarray[val];
cout << endl;
}
}
And the it has printed out:
-887974872
32767
4196400
0
0
0
4196000
0
The question is I thought the default value for array without initialization (in this case its size is 8) would be (0,0,0,0,0,0,0,0). But there seemed to be some weird numbers there. Could anyone tell me what happened and why?
The elements are un-initialized, i.e, they contain garbage value.
If you want to initialize the array elements to 0, use this:
int myarray[8] = {};
Initial values are not guaranteed to be 0.
If you want to get a array have a initial value,you can do like this:
int *arr = new int[8]();
int myarray[8];
This is a simple declaration of an Array i.e you are telling the compiler "Hey! I am gonna use an integer array of size 8". Now the compiler knows it exists but it does not contail any values. It has garbage values.
If you intend to initialize array (automatically) then you need to add a blank initialization sequence.
int myarray[8]={}; //this will do
Happy Coding!