following code set the value of n and K to zero why this happens??
#include <iostream>
#include <stdio.h>
using namespace std;
int main()
{ int n,K;
cin>>n>>K;
cout<<n<<" "<<K<<endl;
int arr[n];
int ranged = (1<<n);
int dp[K][ranged];
for(int i=0;i<n;i++)
{ for(int j=0;j<ranged;j++)
dp[i][j]=0;
}
cout<<n<<" "<<K<<endl;
}
for input
5 3
output:
5 3
0 0
Your code doesn't set the value of n and K to zero, you just set the 2D array dp to 0 inside the for loop. Moreover you create
int dp[K][ranged];
But in for loop you checked for(int i=0;i<n;i++) and assigned dp[i][j]=0; which can buffer overflow.
Change for(int i=0;i<n;i++) to for(int i=0;i<K;i++)
You should most probably get Segmentation Fault. Segmentation fault is a specific kind of error caused by accessing memory that “does not belong to you.”
Your outer for loop goes from 1 to n but the number of rows you declared in your 2D array was K. So as long as n<=K your code should run fine but if you give n>k ( as 5>3 ) then you should get a segmentation fault ( or undefined behaviour as you are getting!).
Either change
for(int i=0;i<n;i++) to for(int i=0;i<K;i++)
or
int dp[K][ranged]; to int dp[n][ranged];
Related
i am running this code in online compiler showing dumped core error this program finding highest product of two pair.
#include <bits/stdc++.h>
using namespace std;
void maximumproductpair(int arr[],int n){
sort(arr,arr+n);
reverse(arr,arr+n);
int prod;
for(int i=0; i<n; i++){
cout<<arr[i];
}
prod=prod*arr[0];
prod=*arr[1];
cout<<prod;
}
int main()
{
int t,n;
int arr[n];
cin>>t;
cout<<"\n";
cin>>n;
cout<<"\n";
while(t--){
for(int i=0; i<n;i++){
cin>>arr[i];
}
}
maximumproductpair(arr,n);
return 0;
}
in code everything fine then why this error?
Mistake 1
The problem is that your t and n variables are uninitialized. This means both t and n have garbage value. And when you wrote:
int t,n;
int arr[n];//UNDEFINED BEHAVIOR because n has garbage value
You have undefined behavior because n has garbage value.
This is why it is advised that
always initialize built in types in local/block scope.
Mistake 2
Second, note that in C++ the size of an array must be a compile-time constant. So take for example the following code snippets:
int n = 10;
int array[n]; //INCORRECT
The correct way to write the above would be:
const int n = 10;
int array[n]; //CORRECT
Similarly,
int n;
cin >> n;
int array[n]; //INCORRECT becasue n is not a constant expression
Also note that some compilers provide compiler extension that lets you have variable length array. You can read more about it at Why aren't variable-length arrays part of the C++ standard?.
If you want to take the size of the array as input from the user then you should use dynamic sized containers like std::vector :
int n;
cin >>n;
std::vector<int> array(n);// CORRECT, this creates a vector of size n of elements of type int
Also see Why should I not #include <bits/stdc++.h>?.
#include <iostream>
using namespace std;
int main() {
int T,D;
long long int N;
long long int a[N];
long long int b[D];
cin>>T;
for(int i=0;i<T;i++)
{
cin>>N>>D;
for(int i=0;i<N;i++)
{
cin>>a[i];
}
for(int i=0;i<D;i++)
{
b[i]=a[i];
}
for(int i=0;i<(N-D);i++)
{
a[i]=a[i+D];
}
for(int i=0;i<D;i++)
{
a[i+N]=b[i];
}
for(int i=0;i<N;i++)
{
cout<<a[i];
}
cout <<endl;
}
return 0;
}
Why is this coding having segmentation fault? I have seen many solution but cann't get it right.On visual studio or any other application it is not working but on gfg it is working. Please help me solve this problem
There are several things that are wrong.
C-style arrays must be set at compile time. So if you want to use int a[N], N must to known at compile time. If you want a flexible array, one C++ way is to use std::vector.
Then the array a goes from 0 to N-1. So going a[N] is going too far. So a[i+N] is way out if bounds and will be segfault.
you declare array a with N element, but use index out of the array range.
long long int a[N]; // declare here, maximum element is N
for(int i=0;i<D;i++)
{
a[i+N]=b[i]; // use index out of array a
}
I am trying to solve the program of array rotation. I am getting segmentation error in the code. Can someone please tell where is the problem in this code?
this is the question
Given an unsorted array arr[] of size N, rotate it by D elements (clockwise).
The first line of the input contains T denoting the number of testcases. First line of each test case contains two space separated elements, N denoting the size of the array and an integer D denoting the number size of the rotation. Subsequent line will be the N space separated array elements.
and i have solved it with the following code.
#include <iostream>
using namespace std;
int* rotate(int ar[],int n, int m)
{static int temp[100];
for(int i =0;i<m;i++)
{
temp[i]=ar[i];
}
for(int j =m;j<n;j++)
{
ar[j-m]=ar[j];
}
int x=0;
for(int k =n-m;k<n;k++)
{
ar[k]=temp[x];
x++;
}
return ar;
}
int main() {
//code
int t, n , m;
cin>>t;
while(t>0)
{
cin>>n>>m;
int arr[n];
int * ptr;
for(int i = 0 ;i<n;i++)
{
cin>>arr[i];
}
ptr=rotate(arr,n,m);
for(int j=0;j<n;j++)
cout<<ptr[j]<<" ";
cout<<endl;
t--;
}
return 0;
}
If m > n then it crashes in the first for() loop in rotate as you index past the end of arr.
If m < 0 it crashes in the 2nd loop as it index before arr.
There are probably more cases.
This is a syntax of a program that I made of hackerrank to reverse an array. The location of the question is Practice < Data Structures < Arrays < Arrays - DS
the program seems to work fine on an online compiler but is showing error over hackerrank.
can anyone guide me where I went wrong?
#include<iostream>
using namespace std;
int main(){
int n,i;
int arr[n];
cin>>n;
for(int i=0;i<n;i++)
{
cin>>arr[i];
}
for(int i=n-1;i>=0;i--)
{
cout<<arr[i];
}
}
You are creating an array with n elements before you read n, i.e n is having garbage value. Here is correct working code.
#include <iostream>
using namespace std;
int main(){
int n,i;
cout<<"Enter number of elements"<<endl; // Comment it if you don't want debug console outut
cin>>n;
int arr[n];
cout<<"Enter "<<n<<" elements"<<endl; // Comment it if you don't want debug console outut
for(int i=0;i<n;i++)
{
cin>>arr[i];
}
for(int i=n-1;i>=0;i--)
{
cout<<arr[i];
}
}
I changed your solution and it work fine now , i will tell you some notes for your future:
1 - You have to read size of array first before declare array as mentioned in comments by #HolyBlackCat , otherwise it will give garbage value.
2 - this command int arr[n]; won't work on all Compilers and may give you an Error. Is there a solution to declare array without specific size ? Yes , you can use Vector like that vector<int> arr(n);but you have to include library of vector first #include<vector>
3 - In C and C++ programs the main function is of type int and therefore it should return an integer value. The return value of the main function is considered the "Exit Status" of the application. On most operating systems returning 0 is a success status like saying "The program worked fine". So you have to write return 0; in the end of your program.
#include<iostream>
#include<vector> // must include to use Vectors
using namespace std;
int main(){
int n;
cin >> n; // Must read size of array first , otherwise it will give it garbude value
vector<int> arr(n); // instead of int arr[n]
for(int i = 0 ; i < n ; i++)
cin >> arr[i];
for(int i = n-1 ; i >= 0 ; i--)
cout << arr[i] << " ";
cout << endl; // to print new line as mentioned in the problem statement
return 0; // Prefer to use it always
}
Hope that helps you and Good Luck.
The exercise of Hacker Rank needs that you reverse an array of integers, might you have a problem with the variable size array, cause some compilers support this characteristic but others not.
And Hacker Rank do not support some properties in other languages like JS , Hacker Rank do not support prompt() for take an input.
In any case for fix this error you can use vector class.
#include<iostream>
#include<vector>//Include library vector for dynamic size of array
using namespace std;
int main(){
int n;
cin>>n;
vector<int> arr(n);//Declare the vector with a max size n
for(int i=0;i<n;i++){
cin>>arr[i];
}
for(int i = n-1 ;i>=0;i--){
cout<<arr[i]<<" ";
}
return 0;
}
This code has passed al test cases of hackerRank
All the test on hackerRank had passed
When I try to compile the below code terminal says stack smashing detected abc2 terminated Aborted (core dumped). This error shows when for loop going through the two dimensional array.
What I want to do is get user input to first column using cin>>arr[0][i]; and 0 for every other columns usingarr[i+1][r]=0;.
#include <iostream>
using namespace std;
void displayArray(int arr[][4],int row,int col);
int main(){
int arr[3][4];
for(int i=0;i<4;i++){
cout<<"enter value ";
cin>>arr[0][i];
for(int r=0;r<3;r++){
arr[i+1][r]=0;
}
}
displayArray(arr,3,4);
return 0;
}
void displayArray(int arr[][4],int row,int col){
for(int i=0;i<row;i++){
for(int r=0;r<col;r++){
cout<<arr[i][r]<<" ";
}cout<<endl;
}
}
You are going beyond the bounds of your array here:
int arr[3][4];
for(int i=0;i<4;i++){
//...
arr[i+1][r]=0; // <-- i+1 when i == 2 is going to give trouble
//...
}
If i >= 2, you're writing to arr[3], arr[4], etc. This is a memory overwrite and the behavior then becomes undefined.
Obviously the fix is either to throttle the loop back so that i is always less than 2, or your array's first dimension needs to be increased from 2 to a bigger number.