C/C++ :: Comparing Pointer To Variable As While Loop Condition
Aug 11, 2014
I'm writing a delete function for a linked list, and I'm having issues with this bit of code:
void deleteNode(int data){
node* del = NULL;
t = h;
n = h;
while(n != NULL && n->_data != data){
t = n;
n = n->next;
}
}
Or more precisely, this portion:
&& n->_data != data
n is my new node variable, _data is the storage variable in the private section of my class, and data is the information being searched for that needs to be deleted. Everything works without this section of the code. My assumption is that n->_data is somehow wrong, but I don't see how. I've tried everything I can think of- using parenthesis, using the variable rather than the pointer, I've tried expressing the pointer in a different way, I've tried using my t variable rather than n, and I've found examples online that use this exact same expression without any issues.
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Jan 14, 2014
I am getting and infinite loop for loop pointer variable current which points to head and is incremented by current->next in while loop. I use the pointer variable the same way in my display routine and it works. Here is listing of code.
#include "stdafx.h"
#include<iostream>
struct node{
int data;
node *next;
[Code] .....
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Oct 6, 2014
I've written a bit of code :
#include <iostream>
#include <cmath>
#include <cstdio>
int main() {
for(int i=1; i<=1000; i++)
for(int j=i+1; j<=1000; j++)
for(int k=j+1; k<=1000; k++)
[Code] ...
Now why does defining the if condition as if(pow(i,2) + pow(j,2) == pow(k,2)) doesnt work (ie. doesn't print anything) while defining it as if(i*i + j*j == k*k) works flawlessly - by working I mean printing out single set of 3 numbers.
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May 23, 2014
I found a for loop in an example that I don't understund fully.
Code:
for (i=64; i; i/=2)
printf("i: %d
",i);
Now this is dividing by 2 until it reach '1' and stops. But why does this stops?
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Dec 8, 2014
The while loop part of my program isn't working right. stringOriginal is an array. If a large amount of characters passed the max 80 im processing is typed, it goes into a infinite loop. Also the condition doesn't work i type in quit and the loop continues.
while(stringOriginal != "quit"){
std::cout << "Enter a string of characters you would like to reverse
";
cin.getline(stringOriginal,79,'
');
}
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Oct 26, 2013
I need to do make a loop inside a condition. Can it be done? I don't want to call another function to do it. Any way at all without calling separate function inside the if? I just want to do:
if (
for (int i = 0; i<=10; i++)
{
//stuff related to the for loop
} )
{
//stuff related to the initial if condition
};
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May 18, 2013
Write a program to calculate the Loan Balance, where a person borrows an amount A and in return he/she agrees to make N payments per year, each of amount P. While the person is repaying the loan, interest will accumulate at an annual percentage rate of R, and this interest will be compounded N times a year (along with each payment). Therefore, the person must continue paying these installments of amount P until the original amount and any accumulated interest is repaid.
NOTE: The formula to calculate the amount that the person needs to repay after T years is-
Balance Amount after T years = A[(1+R/N)^NT]-P
-----------------------------------------------------------
I have a few doubts :
1. I think that the "balance amount" formula can directly give the "loan balance" for the person. I'm not sure if it's correct but in that case the question would serve no purpose. Maybe I'm wrong.
2. If there should be a loop to calculate the loan balance, what condition should I give and which loop will be better to use?
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Mar 25, 2013
I am trying to make a game where you have a secret code that is coded with colors like ROYG (red,orange,yellow,green) and I am having trouble when it tells you when you have a right color in the right spot or a right color in the wrong spot when you guess a color. How can I change my code under the function int comparearray where it will compare pointers to pointers and not integers and give me the correct number of "almost" and "correct".
Code:
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#define ROWS 100
#define COLS 4
}
[code]....
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Oct 14, 2013
I am trying to compare a math operator with a variable, but i keep getting this error:
postfixDriver.cpp:93: error: expected primary-expression before ')' token.
I'm sure it's probably something simple, but im just not seeing it. Here is the code snippet:
while (strlen(str) != 0) {
split (str, token);
Postfix stack;
double a;
double b;
double answer;
if (atof(token)==0.0)
[Code] .....
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May 12, 2014
So, I have the beginnings of a rock paper scissors game which i have created before in Java, and i am attempting to create it in c++.
Problem is, the function "int checkConvertInput" containing a loop to make sure input is valid, is not exiting the loop. As far as i can see the two strings are not comparing. Is there a library function for this? I know C had strcmp but i am not sure if it applies here.
#include <iostream>
#include <string>
#include <vector>
using namespace std;
int checkConvertInput(int playerSign, string signs[]);
[Code] ....
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Jul 13, 2013
I have function that looks like this myfoo(char* Name) Now i want to compare this name to another one . But the another name is a pointer . This my code :
bool Tribe::RemoveSurvavior(char *H_Name) {
const char *p;
p=SurpointArr[i]->GetSurvivor_Name();
}
I need to compare if p is same as H_Name.
Mine is do it with for on each element but when i use sizeof it gives me size of char and not real size of the name.
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Apr 28, 2015
I have two questions that are related to each other. The first one is about overloading the addition operator.
I have defined a struct as the following:
Code:
#include <iostream>
#include <string>
struct Sales_data {
[Code] ....
I then overloaded the I/O operators so I could print to the screen information related Sales_data.
Code:
// overload ostream in order for cout to work
std::ostream& operator << (std::ostream & out,
const Sales_data & cSales_data) {
out << cSales_data.bookNo << ", " << cSales_data.units_sold << ", "
[Code] ....
My first issue is with overloading the addition operator. Everyone works correctly except for std::cout << item << std:endl; will no not output the ISBN number only the units_sold and revenue when added together.
Code:
// addition operator rules
Sales_data Sales_data::operator + (const Sales_data & data2) {
units_sold += data2.units_sold;
revenue += data2.revenue;
return *this;
}
Now here is the code in its entirety
Code:
#include <iostream>
#include <string>
// Sales_data structure
struct Sales_data {
std:: string bookNo;
unsigned units_sold = 0;
[code] .....
After total = total + item;, I would like to print the total for this particular ISBN. However, I only get: blank, total units, total revenue where blank is where the ISBN would go but doesn't print after addition. My second question has to do with comparing the ISBN's of the books entered during the while loop. I would like to do something like
Code:
if (item_i.bookNo == item_i+1.bookNo) {
total = total + item;
} else {
std::cerr << "Books entered must have the same ISBNs" << std::endl;
}
Unfortunately, I cannot figure out how to set up a comparison of the bookNos. If I used #include <casset> in the overload + rule, it will immediately exit since I have no way to compare the ISBNs.
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Sep 8, 2013
I have to write a loop assigning a variable x to all positions of a string variable and I'm stuck. I don't have extensive experience with arrays and I'm also a bit confused about C-String. The problem is below.
"Given the following declaration and initialization of the string variable, write a loop to assign 'X' to all positions of this string variable, keeping the length the same.
char our_string[15] = "Hi there!";
(Please note this is a 'C-string', not C++ standard string.)"
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Apr 19, 2014
I'm making a system like twitter for class called ShoutOut.com I want to be able to get the PublicShoutOut pointer pointed to by the start iterator and assign it to firstShoutOutToDisplay and secondShoutOutToDisplay because I need that in order to pass the pointers to one of my functions. When I step through the debugger the values in start are all default values like "" and so are the values in this->firstShoutOutToDisplay but the message that start points to is being output just fine.
EDIT: got rid of irrelevant code. Am I using the correct syntax to do this?
if (start != finish) {
//getting these because a shoutout needs to be passed to the function that displays
//options for a shoutout
this->firstShoutoutToDisplay = (*start);
[Code] ....
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Feb 6, 2013
I'm writing a program to sum up the even numbers in between 1 and 100, using a while loop. At the beginning of my program, I initialize a variable "sum" to 0, and a variable "temp" to 1. Afterwards I enter a loop where I determine if "temp" is even or not, and if so add it to sum. However, at the end of my program, when I print "sum", I get a result of 0. Below is my code.
Code:
#include <stdio.h>
int main(void)
{
int sum = 0, temp = 1;
}
[code]...
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Jan 19, 2014
for (int raw1=0;raw1<4;raw1++){
for (int column2=0;column2<4;column2++){
unsigned char temp=0x00;
for (column1=0;column1<4;column1++){
int z1=7;
int p1[8]={00000000};
unsigned char temp2;
[Code] ....
When I print the variable output_mix_column inside the for loop as shown in the code, it prints the right output, but when I print it outside the for loop, it changes its value ....
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Dec 18, 2014
what happens to pointer pt when string s is reallocated to accommodate bigger size? does it updates itself or does it points to previous s which is not used anymore?
#include <iostream>
#include <string>
using namespace std;
int main() {
string s= "aa";
[Code] ....
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Aug 1, 2013
Code:
#include <stdio.h>
int main(void){
int a=0;
for(;a<=10;)
int b;
return 0;
}
I have got a code like this. I don't expect to get an output but just assumed I would see the command screen until I terminated it. What I want to do is just declare a variable b in a endless loop. But what I got from the compiler is this error: error: expected expression before 'int'. I am using Code::Blocks and I think the compiler is GCC.
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Apr 28, 2013
I have a problem with my code which I can't work out:
double Mi = 200*pow(10,30);
cout << "
Enter accreted mass increment in solar masses
";
cin >> dm;
cout << "
[Code] ....
Basically the loop works, but gives the wrong results.
I need, at the end of the loop, to sort of "redefine" Mi as "Mi + Macc". I then need it to repeat the loop, and at the end add another Macc so that Mi becomes "Mi + Macc + Macc", etc.
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Mar 25, 2013
This code is used in scientific calculation for optimization problem.
Basically a particle is moving in a three dimensional space, its position is (x,y,z).
At each position, there is a fitness value associated with that position.
The fitness value is given by fitness(x,y,z) (code line 12~19).
We need to find out, when the particle moves around randomly, what is the highest possible fitness value.
To solve this, below code is used, and it produces correct result.
#define DIMENSION 3
#define MAXX 4
#define MINX 0
#define MESHsize 1
#include <iostream>
using namespace std;
float maxValue = 0.0;
[Code] ....
The output of the code:
[ fitness(0,0,0) = 0] [ fitness(0,0,1) = 1] [ fitness(0,0,2) = 4] [ fitness(0,0,3) = 9]
[ fitness(0,1,0) = 1] [ fitness(0,1,1) = 2] [ fitness(0,1,2) = 5] [ fitness(0,1,3) = 10]
[ fitness(0,2,0) = 4] [ fitness(0,2,1) = 5] [ fitness(0,2,2) = 8] [ fitness(0,2,3) = 13]
[ fitness(0,3,0) = 9] [ fitness(0,3,1) = 10] [ fitness(0,3,2) = 13] [ fitness(0,3,3) = 18]
..... so on
Answer: highest fitness = 27
Note: In this case, the values of x,y and z is integers from 0 to 3 inclusive.
For 3-dimensional space above, actually the code had run through 3 nested "for" loops.
Question: Above code works for 3-dimensional space. How to generalize the code, so that it works also for N-dimensional space, where N is an arbitrary integer?
( Note: possibly N = 30 )
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Feb 7, 2015
I want to create a loop that that generates a random number set and gives the user the option to run the loop again for a new number. I have that working but when the loop ends the variable value does not leave the loop. I tried a posttest and pretest loop.
Is it possible to declare/create/alter a variable in a loop and have that value exit the loop to use in the code later? I am still learning about global variables.
#include <iostream>
#include <cstdlib>
#include <ctime>
#include <string>
int oneDiceSix() // Roll 1d6
{int oneDiceSix = 1+(rand()%6);
return oneDiceSix;} //end function
[code]....
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Aug 18, 2014
Should i never return a pointer to a local variable. i have seen the following code in the standard text book.
Code:
struct node *add_to_list(struct node *list, int n)
{
struct node *new_node;
new_node = malloc(sizeof(struct node));
// some code here
return new_node;
}
new_node is a local pointer then why is he returning the new_node? Is it wrong or am i failing to understand something?
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Dec 2, 2013
I am stuck at a problem where I have two pointers pointing to the same object, and I need to change an int on one of the pointers but point to the same object.
To be more specific, there is an array of Item objects. A long list of items a player can buy. Then, there is the player's inventory, a vector pointer. Whenever a player buys an item, it sets the pointer to the bought object.
The problem arises when he buys two of the same object. I tried to identify the objects with an ID, but it does nothing, because they are just pointing to the same object, and so I have no way of telling them apart.
This is further complicated by the fact that it is a polymorphic object. So, I can't simply make a new every time I buy an object, without making a hassle. Well, at least I am not familiar with that kind of code just yet.
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Mar 29, 2014
Suppose you a class declared with a pointer initialization variable. When writing the copy constructor, how would one make a deep copy of the pointer variable? Can it be done in the same manner as automatic variables i.e. in the initialization list or in some other manner?
I am using C++ 11.
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Mar 29, 2012
In the code below:
void test(int * i) {
i = new int;
*i = 10;
cout << "i: " << *i << endl;
[Code] ....
The outuput is:
i: 10
t: (some memory position).
If I really want to allocate an integer variable to t, i need to modify the void test(int * i) procedure to void test(int *& i).
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Nov 3, 2013
I have a simple question. Can a pointer be incremented in a for loop? In my program, I use a pointer variable and use it in a for loop like such:
for(*var1 = 1; *var1<100 ;*var1++)
int function(int* var1) {
if(*var1 blah blah)
{do blah blah}
if(blah)
{blah}
}
}
The variable is not incremented by the ++ even when the if conditions are not met and the loop shouldn't break. the *var1 stays at 1.
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