Frequency of arrays in C++ - c++

I'm trying to write a code which works like this:
it first gets an int from the user which presents the number of array indexes the user would like to own (n), then the code creates an array with n number of indexes. It then has to print the frequency of every entered number.
Running my below code results in a segmentation fault. Any solution will in advance be appreciated.
My code:
int main()
{
int n, index;
cin>>n;
int ar[n];
int freq[100]={0};
for (int i = 0; i < n; i++)
{
cin>>ar[i];
}
for (int i = 0; i < 100; i++)
{
index=ar[i];
freq[index]++;
}
for (int i = 0; i < 100; i++)
{
cout<<freq[i]<<' ';
}
return 0;
}
NOTE: 1<=n<=100

I would do something like this:
int main ()
{
int n, input;
while (n > 100 || n < 1)
cin >> n;
// indexes 0 - 99
int freq[100] = { 0 };
for (int i = 0; i < n; i++)
{
cout << "number: ";
cin >> input;
if (input > 0 && input <= 100)
freq[input - 1]++;
}
for (int i = 0; i < n; i++)
if (freq[i] != 0)
cout << i + 1 << "-->" << freq[i] << &endl;
return 0;
}
try it here

Related

Smallest composite number in array

I am totally new to programming and I am bit stuck on my code. I wrote code where I wanted to find smallest composite number in array(using only low-level arrays). When I wrote down like size of array 3 and enter 1 2 77, than it throws out random 16. Can you explain why is this happening and perhaps give some solution how to fix this.
#include<iostream>
using namespace std;
int fun(int n)
{
int arr[n];
int mini = arr[0];
for (int i = 0; i < n; i++)
cin >> arr[i];
for (int i = 0; i < n; i++)
{
for (int j = 2; j < arr[i]; j++)
{
if (arr[i] % j == 0)
{
if (mini > arr[i])
{
mini = arr[i];
}
else
{
mini = mini;
}
break;
}
}
}
return mini;
}
int main()
{
int n;
cout << "Size of array: ";
cin >> n;
cout << "Write " << n << " numbers: " << fun(n) << endl;
return 0;
}

Count of Maximum , Passing Test cases but WA

Getting error in this code, even though it passed the basic test cases. But still, it gives the wrong answer.
Cannot find the test case where it fails, Solution to Codechef Count of maximum problem. I think a part of the code is making it fail for a certain test case(s).
Can anyone help me find the error in this code, please?
#include <bits/stdc++.h>
using namespace std;
int main()
{
int k;
cin >> k;
for (int j = 0; j < k; j++)
{
int n;
cin >> n;
int a[n];
for (int i = 0; i < n; i++) {
cin >> a[i];
}
int maxCount = 0;
int number;
int index = 0;
for (int i = 0; i < n; i++)
{
int count = 0;
for (int l = 0; l < n; l++)
{
if (a[i] == a[l])
{
count++;
if (count > maxCount)
{
maxCount = count;
index = i;
}
if (count == maxCount) {
(a[i] > a[index]) ? number = a[index] : number = a[i];
}
}
}
}
cout << number << " " << maxCount << endl;
}
}
Your number variable is redundant. You need to track theindex of the elements in the array.
That means, change this line
(a[i] > a[index]) ? number = a[index] : number = a[i];
to
(a[i] > a[index]) ? index = index : index = i;
and print
std::cout << a[index] << " " << maxCount << std::endl;

How do I put any value X after all the minimums in an array?

If I enter an array , at first the code finds the minimums then I want to put zeroes after all the minimums . For example
given an array = 1,1,3,1,1
As we see 1s are the minimum so the result should be = 1,0,1,0,3,1,0,1,0
CODE
#include <pch.h>
#include <iostream>
int main()
{
int min = 10000;
int n;
std::cout << "Enter the number of elements (n): "; //no of elements in the
std::cin >> n; //array
int *array = new int[2 * n];
std::cout << "Enter the elements" << std::endl;
for (int i = 0; i < n; i++) {
std::cin >> array[i];
if (array[i] > min)
min = array[i];
}
for (int i = 0; i < n; i++) {
if (array[i] == min) { // Not very clear about this
for (int k = n; k > i; k--) // part of the code, my teacher
array[k] = array[k - 1]; //explained it to me , but i
array[i + 1] = 0; // didn't understand (from the
i++; // `for loop k` to be precise)
n++;
}
std::cout << array[i] << ", 0";
}
return 0;
}
But my answer doen't put zeroes exactly after minimums
There are few issues in your code, first of all your min is wrong. I have fixed your code with comments on fixes I have made. Please take a look :
#include "stdafx.h"
#include <iostream>
int main()
{
int min = 10000;
bool found = 0;
int n;
std::cout << "Enter the number of elements (n): "; //no of elements in the
std::cin >> n; //array
int *array = new int[2 * n];
std::cout << "Enter the elements" << std::endl;
for (int i = 0; i < n; i++) {
std::cin >> array[i];
if (array[i] < min) //< instead of >
min = array[i];
}
for (int i = 0; i < n; i++) {
if (array[i] == min)
{
for (int k = n; k > i; k--)
{
array[k] = array[k - 1];
}
array[i + 1] = 0;
i++; //increment i here because you don't want to consider 0 that you have just added above.
n++; //since total number of elements in the array has increased by one (because of 0 that we added), we need to increment n
}
}
//print the array separately
for (int i = 0; i < n; i++)
{
std::cout << array[i];
if (i != n - 1)
{
std::cout << ",";
}
}
return 0;
}
The first issue was in the calculation of min: < instead of >.
Another problem if that you are modifyng the paramers iand ninside the loop. This is rather dangerous and implies to be very cautious.
Another issue was that it should be i++; n++; instead of i--,n--;
Here is the code:
// #include <pch.h>
#include <iostream>
int main()
{
int min = 1000000;
int n;
std::cout << "Enter the number of elements (n): "; //no of elements in the
std::cin >> n; //array
int *array = new int[2 * n];
std::cout << "Enter the elements" << std::endl;
for (int i = 0; i < n; i++) {
std::cin >> array[i];
if (array[i] < min)
min = array[i];
}
for (int i = 0; i < n; i++) {
if (array[i] == min) { // Not very clear about this
for (int k = n; k > i; k--) // part of the code, my teacher
array[k] = array[k - 1]; //explained it to me , but i
array[i + 1] = 0; // didn't understand (from the)
i++;
n++;
}
}
for (int i = 0; i < n; i++) {
std::cout << array[i] << " ";
}
std::cout << "\n";
return 0;
}

How do I get this random number generator out of an infinite loop?

I have an assignment for school where I need to create a lottery program. It is supposed to allow the user to input six numbers and then generate six random numbers for comparison. I got the inputs working, but I have encountered a problem where the random number generator (located in the while loop) is stuck in an infinite loop, and I have absolutely no idea what is causing it since I have never had an infinite loop in any previous programs. If someone could please look through the code and possibly establish what is wrong, I would greatly appreciate it.
#include<iostream>
#include<time.h>
using namespace std;
void randomizeSeed();
int randomRange(int min, int max);
int getInteger();
int main()
{
randomizeSeed();
const int minNumber = 1;
const int maxNumber = 49;
const int Size = 6;
int luckyNumbers[6] = {};
int randomNumber = randomRange(minNumber, maxNumber);
int winningNumbers[6] = {};
cout << "Enter six numbers between 1 and 49...\n";
{
for (int i = 0; i < Size; i++)
{
luckyNumbers[i] = getInteger();
}
for (int i = 0; i < Size; i++)
{
for (int i = 0; i < Size - 1; i++)
{
if (luckyNumbers[i] > luckyNumbers[i + 1])
{
int temp = luckyNumbers[i];
luckyNumbers[i] = luckyNumbers[i + 1];
luckyNumbers[i + 1] = temp;
}
}
}
cout << "Lucky Numbers: ";
for (int i = 0; i < Size; i++)
{
cout << luckyNumbers[i] << " ";
}
cout << "\n";
cout << "Press any button to see the Winning Numbers.\n";
system("pause");
bool exist = true;
while (exist == true)
{
int count = 0;
cout << "Winning Numbers: ";
for (int j = 0; j < 6; j++)
{
winningNumbers[j] = randomRange(1, 49);
cout << winningNumbers[j] << " ";
system("pause");
}
}
}
}
void randomizeSeed()
{
srand(time(NULL));
}
int randomRange(int min, int max)
{
int randomValue = rand() % (max + 1 - min) + min;
return randomValue;
}
int getInteger()
{
int value = 0;
while (!(cin >> value) || (value >= 50) || (value <= 0))
{
cin.clear();
cin.ignore(numeric_limits<streamsize>::max(), '\n');
}
return value;
}
for (int i = 0; i < Size; i++)
for (int i = 0; i < Size - 1; i++)
if (luckyNumbers[i] > luckyNumbers[i + 1])
{
int temp = luckyNumbers[i];
luckyNumbers[i] = luckyNumbers[i + 1];
luckyNumbers[i + 1] = temp;
}
You have two loops and they both use i. You probably mean to use the second loop with another variable name, for example:
for (int i = 0; i < Size; i++)
{
for (int k = 0; k < Size - 1; k++)
{
if (luckyNumbers[i] > luckyNumbers[k + 1])
{
int temp = luckyNumbers[i];
luckyNumbers[i] = luckyNumbers[k + 1];
luckyNumbers[k + 1] = temp;
}
}
}
If you set your compiler warning level to 4 then compiler should warn you about these errors. Try to resolve all compiler warnings.

Incorrect Result from Selection Sort Algorithm

#include <iostream>
using namespace std;
// Selection Sort function.
// Parameter 'a' is the size of the array.
void ss(int AR[] , int a) {
int small;
for (int i = 0 ; i <a ; i++) {
small = AR[i];
for (int j = i+1 ; j <a ; j++) {
if (AR[j]< small) {
int k = AR[j];
AR[j] = AR[i];
AR[i] = k;
}
}
}
}
int main() {
cout << "Enter the size of Your Aray";
int a;
cin >> a;
int AR[a];
cout << endl;
for (int i = 0; i < a; i++) {
cin >> AR[i];
cout << endl;
}
ss(AR, a);
cout << "The Sorted Array is";
for (int i=0; i < a; i++) {
cout << AR[i] << " ";
cout << endl;
}
}
When I enter the following:
15
6
13
22
23
52
2
The result returned is:
2
13
6
15
22
23
52
What is the bug preventing the list from being sorted numerically as expected?
The function can look like
void ss ( int a[], size_t n )
{
for ( size_t i = 0 ; i < n ; i++ )
{
size _t small = i;
for ( size_t j = i + 1; j < n ; j++ )
{
if ( a[j] < a[small] ) small = j;
}
if ( i != small )
{
int tmp = a[small];
a[small] = a[i];
a[i] = tmp;
}
}
}
It doesn't seem to be the SelectionSort I know. in the algorithm I know during every loop I look for the smallest element in the right subarray and than exchange it with the "pivot" element of the loop. Here's the algorithm
void selectionSort(int* a, int dim)
{
int posMin , aux;
for(int i = 0; i < dim - 1; ++i)
{
posMin = i;
for(int j = i + 1; j < dim; ++j)
{
if(a[j] < a[posMin])
posMin = j;
}
aux = a[i];
a[i] = a[posMin];
a[posMin] = aux;
}
}
and it seems that you change every smaller element you find, but also change the position of the "pivot". I hope the answer is clear.
Everything is ok in the original function, only that the small variable need to be refreshed when two vector elements will be switched.
Also in if statement set the small variable to the new value of AR[i].