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char arr[10]="\0",arr1[2][5]={'\0'};
cout<<"enter the full line : ";
gets(arr);
for (int i=0;i<1;i++)
{
for (int j=0;j<10;j++)
{
if(j<=4)
{
arr1[0][j]=arr[j] ;
}
else if (j>4)
{
arr1[1][j-5]=arr[j] ;
}
}
}
for(int j=0;j<5;j++)
{
cout<<arr1[0][j]<<" ";
}
cout<<endl;
for(int j=0;j<5;j++)
{
cout<<arr1[1][j]<<" ";
}
Here what i am trying to do is converting a 1d array in to 2d array.
my main purpose is to store 1d array on a 2d and when the first row is completed it should shift the string to next row it is doing all the as i have declared the arr[10] and inputting 10 charcter string through get(arr) it is storing the array as i want but at the end displays an error window i dont know why the program is running perfect as well as giving this error window
my input : hanzlaamja (10charcters)
my output:
h a n z l
a a m j a
according to my wish but the main problem is the error window.
note : there is nothing in error box or warning box.
My program is working perfectly, but i am getting an error of array corruption.
Can anybody help me out? I would be very thankful
please see this error message
full picture
The problem is that you read in 10 characters (e.g. "hanzlaamja") and the string termination character '\0', which is automatically added by gets. Thereby you exceed array bounds, as this would require space for 11 characters. So it would already work if you wrote char arr[11];. But as mentioned in the comments, do not use gets; it is unsafe and it does not prevent you from exceeding array bounds. The following snippet shows how to do this part better:
...
char arr[11]="\0",arr1[2][5]={'\0'};
cout<<"enter the full line : ";
// gets(arr);
if (!fgets(arr,11,stdin)) {
cout << "no value read." << endl;
return 1;
}
...
A lot of your loops could be written shorter / better readable. But that's not the actual topic.
Adding to the great point pointed out by #Stephan Lechner, I have composed a solution "as close as possible" to your original.
Compiled under visual studio 2017.
#include "stdafx.h"
#include <iostream>
using namespace std;
int main(int argc, char** argv)
{
cout << "main - start" << endl;
const size_t numOfRows = 2;
const size_t numOfCol = 5;
const size_t numCharsInSingleDimArray = 10;
char arr[numCharsInSingleDimArray] = { '\0' }, arr1[numOfRows][numOfCol] = { '\0' };
cout << "enter the full line : ";
gets_s(arr); // Note:If the buffer (arr) is too small to contain the input line and null terminator, these functions invoke an invalid parameter handle.
cout << "main - entered:" << arr << endl;
char* twoDimArrStartLoc = &(arr1[0][0]); // as user4581301 pointed out, it is also possible to "approach" it by treating the two dimensional array as a contiguous bytes in memory
for (size_t i = 0, j = 0; i< numCharsInSingleDimArray; ++i, ++j)
{
twoDimArrStartLoc[j] = arr[i];
}
cout << "main - after converting the 1d array into 2d array, arr1 is:" << endl;
for (size_t i = 0; i < numOfRows; ++i)
{
for (size_t j = 0; j < numOfCol; ++j)
{
cout << "arr1[" << i << "]" << "[" << j << "]:" << arr1[i][j] << " ";
}
cout << endl;
}
// for debug - you can remove this if not needed...
cout << "main - end, enter any key and press enter to terminate..." << endl;
char tmp;
cin >> tmp;
return 0;
}
Hope it helps.
Cheers,
Guy.
thank you everyone for your support the MAIN mistake i was doing is the use of gets(arr) and doing arr[10] as if you are using function gets(arr) you have to give one extra index which is used by this function gets(arr) i.e. arr[11]
solved :)
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I read array from the text file and I want to copy this array's elements to another text file
#include <iostream>
#include <fstream>
using namespace std;
int main()
{
const int ARRAY_SIZE = 5;
int numbers[ ARRAY_SIZE];
int count = 0;
cout << "1. before opening file\n";
ifstream inputFile;
inputFile.open("test.txt");
if (!inputFile)
{
cout << "error opening input file\n";
return 1;
}
cout << "2. after opening file\n";
cout << "3. before reading file, count = " << count << '\n';
while (count < ARRAY_SIZE && inputFile >> numbers [ count])
count++;
inputFile.close();
cout << "4. after reading file, count = " << count << '\n';
cout<< "The numbers are : ";
for (int i = 0; i < count; i++)
cout << numbers[i] << " ";
cout<< endl;
cout << "5. Program ending" << endl;
return 0;
}
I added this code but it doesn't work. How can I copy this array's elements to destination.txt file?
ofstream fstreamFile("destination.txt");
copy(
numbers,
numbers + sizeof(numbers),
ostream_iterator<int>(fstreamFile)
);
my elements are 10,20,30,40 but in the destination.txt file, output is "10203040160641613632767-1973944304-...."
The problem is that you use sizeof for the end "iterator" of the array.
The sizeof operator returns the size in bytes, not in array elements. That means you will go way out of bounds beyond the end of the array.
I suggest you change to use the standard std::begin and std::end helper functions to get the "iterators" for the array:
std::copy(std::begin(numbers), std::end(numbers), ...);
For proper arrays (but not for pointers, and remember that arrays decays to pointers very easily) those functions will do the right thing.
I am trying to output the values present in the array, that are accepted during runtime, onto the console. But when I run this program I get the 5 values in the array as the last value only.
For example: if i give 0 1 2 3 4 as the five values for this program then the output is shown as 4 4 4 4 4.
#include "stdafx.h"
#include<iostream>
using namespace std;
int main()
{
int arrsize = 5;
int *ptr = new int[arrsize];
*ptr = 7;
cout << *ptr << endl;
cout << "enter 5 values:";
for (int i = 0; i < arrsize; i++)
{
cin >> *ptr;
cin.get();
}
cout << "the values in the array are:\n ";
for (int i = 0; i < arrsize; i++)
{
cout << *ptr << " ";
}
delete[] ptr;
cin.get();
return 0;
}
Both of your loops:
for (int i = 0; i < arrsize; i++)
...
loop over a variable i that is never used inside the loop. You are always using *ptr which refers always to the first element of the dynamically allocated array. You should use ptr[i] instead.
A part from that, dynamic allocation is an advanced topic. I'd recommend sticking with simpler and more commonly used things first:
std::cout << "Enter values:";
std::vector<int> array(std::istream_iterator<int>(std::cin), {});
std::cout << "\nThe values in the array are:\n";
std::copy(begin(array), end(array), std::ostream_iterator<int>(std::cout, " "));
Live demo
Following issues I think you could tackle:
The first include can be omitted I think. Your code works without that.
You use cin.get(), not sure why you need that. I think you can remove that. Even the one at the very end. You could put a cout << endl for the last newline. I am using Linux.
And use ptr like an array with index: ptr[i] in the loops as mentioned in the other answer. ptr[i] is equivalent to *(ptr+i). You have to offset it, otherwise you're overwriting the same value (that is why you get that result), because ptr points to the first element of the array.
P.S.: It seems that if you're using Windows (or other systems) you need the cin.get() to avoid the console to close down or so. So maybe you'd need to check it. See comments below.
I am basically trying to store everything after a certain index in the array.
For example, I want to store a name which is declared as char name[10]. If the user inputs in say 15 characters, it will ignore the first five characters and store the rest in the char array, however, my program crashes.
This is my code
char name[10];
cout<< "Starting position:" << endl;
cin >> startPos;
for(int i= startPos; i< startPos+10; i++)
{
cout << i << endl; // THIS WORKS
cout << i-startPos << endl; // THIS WORKS
name[i-startPos] = name[i]; // THIS CRASHES
}
For example, if my name was McStevesonse, I want the program to just store everything from the 3rd position, so the end result is Stevesonse
I would really appreciate it if someone could help me fix this crash.
Thanks
Suppose i is equal to 3. In the last iteration of the loop, i is now equal to 12, so substituting 12 in for i, your last line reads
name[12-startPos] = name[12];
name[12] is out of bounds of the array. Based on what you have shown so far, there is nothing but garbage stored in name anyway before you start doing this assignment, so all you're doing is reorganizing garbage in the array.
Please in future: post full compilable example.
A simple answer is that your array maybe is out of bound, since you don't provide full example its hard to know exactly.
Here is a working example:
#include <iostream>
using namespace std;
int main() {
int new_length, startPos;
int length = 15;
char name[15]= "McStevesonse";
cout<< "Starting position:" << endl;
cin >> startPos;
if(new_length <1){ // you need to check for negative or zero value!!!
cout << "max starting point is " <<length-1 << endl;
return -1;
}
new_length=length-startPos;
char newname[new_length];
for(int i= 0; i<new_length; i++){
newname[i] = name[i+startPos]; // THIS CRASHES
}
cout << "old name: " << name << " new name: " << newname << endl;
return 0 ;
}
To put it simply, change this:
for(int i= startPos; i< startPos+10; i++)
To this:
for(int i= startPos; i<10; i++)
You should be fine with that.
Explanation:
At some point, when you use the your old loop, this name[i-startPos] = name[i] would eventually reach an array index out of bounds and causes the crash.
Don't forget to clean up/hide the garbage:
Doing so, would cause the output to produce some kind of garbage outputs. If you got a character array of 'ABCDEFGHIJ', and have chosen 3 as the starting position, the array would be arranged to 'DEFGHIJHIJ'. In your output, you should atleast hide the excess characters, or remove by placing \0's
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I am trying to get the greatest value from the array and its index number also by using a function maxin but my logic somehow isn't working?
#include <iostream>
#include <conio.h>
#include <proceass.h>
void maxin(double[], int);
void main()
{
const int k = 10;
int l = 0;
double num[k];
for (int j = 0; j < k; j++)
{
cout << "Enter the number " << j + 1 << " = ";
cin >> num[j];
if (cin.fail())
{
cout << "Wrong data entered " << "\nTry again";
getch();
exit(0);
}
}
maxin(num, l);
cout << "The Greatest number is = " << num;
cout << "\nIt is " << l << "th number";
getch();
}
void maxin(double k[], int p)
{
int l, s;
l = 10;
s = 0;
double m;
for (int n = 0; n < l; n++)
{
if (k[s] > k[n++])
{
m = k[n];
}
else
{
m = k[n++];
s = ++;
}
}
p = s;
k[s] = m;
}
Your maxin function is invoking Undefined Behavior on your program for causing access to areas beyond the bounds of the array k. This happens because not only is n incremented in the for loop statement, but again in the if statement which is evaluated on each iteration as well. This also happens in the else statement, which is another case of the problem.
When n is 1 less than l, n++ will be >= l, and subsequently dereferencing that address, k[n++], will cause Undefined Behavior. After that, anything can happen to your program, including valid or invalid side effects.
When finding the maximum/minimum value in an array, a variable is usually set to an arbitrary value in the array (typically the first index), and then iteration is performed to check if any other value in the array is smaller/larger than that variable. When that condition passes, the variable is set to the new value in the array.
Furthermore, since you said you needed to set the variable to the index at which the largest value was found, it is necessary that you pass p by reference.
The STL approach:
vector< double > v = {1,2,3,4,5};
auto maxElemIter = std::max_element(begin(v), end(v));
cout << "Max is: " << *maxElemIter;
cout << ", at index: " << distance(begin(v), maxElemIter) << endl;
(I know, this is a cruel suggestion, given code as stated in question above...)
So I am trying to delete duplicate chars in a partially filled array. The array is populated from a file located on my PC. My array population method is working fine; however, my duplicate deleting method is not. Here is my method:
void deleteRepeated(char array[], int* numberUsed)
{
for (int x = 0; x < *numberUsed ; x++)
{
cout << "Positions used: " << *numberUsed << endl;
for (int y = x+1; y < *numberUsed; y++ )
{
cout << "Positions used: " << *numberUsed << endl;
if (array[y] == array[x])
{
cout << "Positions used: " << *numberUsed << endl;
for (int z = y; z < *numberUsed; z++)
array[z] = array[z+1];
y--;
*numberUsed--;
cout << "Positions used: " << *numberUsed << endl;
}
}
}
}
I am passing the entire array, and the number of indices used in that array. The array length is 10, and my tests, I am using 6 out of those 10 with the chars: {'g', 'g', 'n', 'o', 'r', 'e'}. What am I doing wrong?
NOTE: "cout << "Positions used: " << *numberUsed << endl" is being used to check if the method is correctly deleting or not. In the most inner loop where index is z, is where the method starts to go bonkers.
Any help would be much appreciated.
(I wrote the first part of this answer before I read your comment about STL not being allowed, but I'll leave it anyways because I think it's rather neat code.)
You could use the functionality that the C++ standard library makes available to you. Use std::string instead of char arrays (that's nearly always a good idea), then you can do the following (note: C++11 only because of unordered_set and std::begin):
#include <string>
#include <unordered_set>
#include <iostream>
#include <iterator>
std::string uniquechars(const std::string& s) {
std::unordered_set<char> uniquechars(std::begin(s), std::end(s));
std::string newstring(std::begin(uniquechars), std::end(uniquechars));
return newstring;
}
int main() {
std::string teststr("thisisanexamplesentence");
std::cout << "The unique characters of " << teststr << " are " << uniquechars(teststr) << std::endl;
}
Note that it doesn't keep the original order of the characters though, so if that's needed this does not work.
If you have to work without the standard library, you have to dig a bit deeper. #TimChild above already made a good start diagnosing what's wrong with your program, but there are more efficient solutions, for example keeping some kind of record of which characters you have already seen. As you're working with chars, I would consider a bit-field that can hold markers (extra overhead of 256/8=32 bytes) or if that's not too much, just a plain array of bools (extra overhead 256 bytes). As the latter is easier to implement and the code is more legible:
void deleteRepeated(char array[], int *numused) {
bool seenthischar[256] = {false};
char *readpointer = &array[0];
char *writepointer = &array[0];
int length = *numused;
for ( ;readpointer <= &array[0] + length; readpointer++) {
if (seenthischar[((unsigned char) *readpointer)]) {
*numused--;
} else {
seenthischar[((unsigned char) *readpointer)] = true;
*writepointer = *readpointer;
writepointer++;
}
}
}
This only has one loop, so it only has to go through the array once, i.e. its time complexity is linear in the length of the input array.
Every time you find a dup you reduce the number chars used
*numberUsed--;
but remember this controlling the first loop index
for (int x = 0; x < *numberUsed ; x++)
so try this
int count =*numberUsed;
for (int x = 0; x < count ; x++)
this way you visit all the original chars in the array.