Finding 3 or more duplicates in array - c++

I need write a program which checks if there are 3 or more matching numbers in an array. My code works fine until there is an array like "2 2 3 3 5 5 4 4 1 1", then it approves that there are 3 or more duplicates in the array which is not true. Maybe someone knows a simple solution which would help me? Or do I need to overwrite my code?
Here is my code:
#include <iostream>
using namespace std;
void funk(int n, int a[], int &kiek);
int main()
{
int n, a[101],kiek=0;
cin >> n;
for (int i = 0; i < n; i++) {
cin >> a[i];
}
funk(n, a, kiek);
if (kiek > 2) {
cout << "TAIP";
}
else
cout << "NE";
}
void funk(int n, int a[], int &kiek)//funkcijos kūnas
{
int j;
for (int i = 0; i < n; i++) {
for (j = i + 1; j < n; j++) {
if (a[i] == a[j])
kiek++;
cout << kiek;
}
}
}
This is the input:
10
2 2 3 3 5 5 4 4 1 1
This is the output I need to get:
NE

The problem that your code has is:
You are comparing any 2 numbers and never reset the counter. So if there is an 1 1, you are increasing the counter. If there is then an 2 2 you are also increasing the counter. And for the final 3 3 you also increase the same counter. Then it is 3. Although there are only 2 same values. This can never work. What you could do is
Read all values
Count the frequency of EACH different value
Check if the frequency of the values
If any of the counts is greater than 2, then show corresponding message
Show count of each value
I will show you the "more-modern" C++ approach and will use C++ algorithms for the below example solution.
First we will get the number of values to work with from the user. We will store the values in a std::vector. And, we use std::copy_n to copy the values from std::cin to our std::vector. For that we will use the std::istream_iterator that will iterate over the elements given by the user. So, we use a simple one-liner to read all values from the user.
Next is the frequency counting. For this we have a standard solution in C++. You will find it in dozens of places in the net. We will use a std::map. The key is the integer that we read into the vector and the value is the counter. With the std::map's index operator [] we add a value to the map, if it is not yet existing. With the ++ we simply do the counting, whether the value was already in the std::map or has just been added. Also this is a very simple one-liner.
Then, we check, if any of the counts is greater than 2. For this we will use the STL algorithm std::any:of with a very simple lambda. With that, we can create your desired result.
Last, but not least, we show all values and their count, if the count is greater than 2. This we do with an ultra simple range based for loop. We extract the values out of the counter-std::map using structered bindings.
Please see:
#include <iostream>
#include <map>
#include <vector>
#include <algorithm>
#include <iterator>
int main() {
// Give instructions
std::cout << "How many values do you want do read? Please specify: ";
// Read the number of values to enter
size_t numberOfValues{ 0U }; std::cin >> numberOfValues;
// Read the given number of values from std::cin
std::vector <int> values(numberOfValues);
std::copy_n(std::istream_iterator<int>(std::cin), numberOfValues, values.begin());
// Count each value
std::map<int, size_t> counter{};
std::for_each(values.begin(), values.end(), [&counter](const int& i) { counter[i]++; });
// Check, if any count is bigger than 2
if (std::any_of(counter.begin(), counter.end(), [](const std::pair<int, size_t> & c) { return c.second > 2; }))
std::cout << "TAIP\n";
else
std::cout << "NE\n";
// Look, if there is any number with a count bigger than 2 and show the result
for (const auto& [value, count] : counter)
if (count > 2) std::cout << value << " --> " << count << "\n";
return 0;
}
I hope this gives you an idea on how this could be done . . .

Related

Minimum number of steps to equalize distinct character of the string [duplicate]

This question already has answers here:
How to find the minimum number of operation(s) to make the string balanced?
(5 answers)
Closed 1 year ago.
I'm trying to write this program that asks for user input of string, my job is to print out the minimum number of steps required to equalize the frequency of distinct characters of the string.
Example
Input
6
aba
abba
abbc
abbbc
codedigger
codealittle
Output
1
0
1
2
2
3
Here is my program:
#include <iostream>
#include <string>
#include <vector>
#include <algorithm>
#include <unordered_map>
using namespace std;
int main()
{
unordered_map<char, int >m;
vector<int> vec1, vec2;
string s;
int n;
cin >> n;
cin.ignore();
for (int i = 0; i < n; ++i)
{
m.clear();
vec1.clear();
getline(cin, s);
for (int i = 0; i < s.size(); i++)
m[s[i]]++;
for (auto itr : m)
vec1.push_back(itr.second);
sort(vec1.begin(), vec1.end());
int mid = vec1[vec1.size() / 2];
int ans = 0;
for (auto itr : vec1)
ans += abs(mid - itr);
vec2.push_back(ans);
}
for (int i = 0; i < vec2.size(); ++i)
cout << vec2[i] << endl;
}
What I tried to do is for each test case:
Using an unordered_map to count the frequency of the characters of the string.
Push the key values of the map to a vector.
Sort the vector in ascending order.
Calculate the middle element of the vector to equalize the distinct characters with as least steps as possible.
The result will add the difference between the middle element with the current element.
Push the result to another vector and print it.
But my result is wrong at test case number 5:
1
0
1
2
3 // The actual result is 2
3
I don't understand why I get the wrong result, can anyone help me with this? Thanks for your help!
The issue is that your algorithm is not finding the optimal number of steps.
Consider the string you obtained an incorrect answer for: codedigger. It has 4 letters of frequency 1 (coir) and 3 letters of frequency 2 (ddeegg).
The optimal way is not to convert half the letters of frequency 2 into some new character (not present in the string) to make all frequency 1. From my understanding, your implementation is counting the number of steps that this would require.
Instead, consider this:
c[o]dedigge[r]
If I replace o with c and r with i, I obtain:
ccdediggei
which already has equalized character frequencies. You will note that I only performed 2 edits.
So without giving you a solution, I believe this might still answer your question? Perhaps with this in mind, you can come up with a different algorithm that is able to find the optimal number of edits.
Your code correctly measures the frequencies of each letter, as the important information.
But then, there were mainly two issues:
The main target value (final equalized frequency) is not necessarily equal to the median value. In particular, this value must divide the total number of letters
For a given targeted height value, your calculation of the number of steps is not correct. You must pay attention not to count twice the same mutation. Moreover, the general formula is different, depending the final number of different letters is equal, less or higher than the original number of letters.
The following code focuses on correctness, not on efficiency too much. It considers all the possible values of the targeted height (frequency), i.e. all the divisors of the total number of letters.
If efficiency is really a concern (not mentioned in the post), then for example one could consider that the best value is unlikely to be very far from the initial average frequency value.
#include <iostream>
#include <string>
#include <vector>
#include <algorithm>
#include <numeric>
#include <unordered_map>
// calculates the number of steps for a given target
// This code assumes that the frequencies are sorted in descending order.
int n_steps (std::vector<int>& freq, int target, int nchar) {
int sum = 0;
int n = freq.size();
int m = nchar/target; // new number of characters
int imax = std::min (n, m);
for (int i = 0; i < imax; ++i) {
sum += std::abs (freq[i] - target);
}
for (int i = imax; i < n; ++i) {
sum += freq[i];
}
if (m > n) sum += m-n;
sum /= 2;
return sum;
}
int main() {
std::unordered_map<char, int >m;
std::vector<int> vec1, vec2;
std::string s;
int n;
std::cin >> n;
std::cin.ignore();
for (int i = 0; i < n; ++i)
{
m.clear();
vec1.clear();
//getline(cin, s);
std::cin >> s;
for (int i = 0; i < s.size(); i++)
m[s[i]]++;
for (auto itr : m)
vec1.push_back(itr.second);
sort(vec1.begin(), vec1.end(), std::greater<int>());
int nchar = s.size();
int n_min_oper = nchar+1;
for (int target = 1; target <= nchar; ++target) {
if (nchar % target) continue;
int n_oper = n_steps (vec1, target, nchar);
if (n_oper < n_min_oper) n_min_oper = n_oper;
}
vec2.push_back(n_min_oper);
}
for (int i = 0; i < vec2.size(); ++i)
std::cout << vec2[i] << std::endl;
}

Get number of same values in arrays in C++

I need a function int countDifferentNumbers(int v[], int n) which counts how many different values the array v with n entries contains.
Example:
It should return the result 3 for the array v = {1, 5, 5, 8, 1, 1} because the array contains only 3 different values.
This is how the code looks like so far:
int countDifferentNumbers(int v[], int n)
{
int counter = 0;
for(int i = 0; i < n; ++i)
{
for(int j = i; j < n; ++j)
{
if(v[i] == v[j + 1])
{
cout << "match" << endl;
counter++;
cout << v[i] << endl;
}
}
}
return counter;
}
I would appreciate an explanation of what is wrong in my function and how I need to redesign it.
Note: Unfortunately, I have not found a suitable thread for this either. All threads with my problems were solved in Java and Python languages.
Recently I see more and more answers here on SO that lead users in the wrong direction by giving bad answers.
Also, for C++, the question has already been answered in the comment by Igor Tandetnik, and that should finally be used.
But let me answer the question of the OP as asked. What is wrong with my function? OK, there are several aspects. Let us first look at the style.
You have 0 lines of comments, so the code quality is 0. If you would write comments, then you would already find most bugs by yourself, because then, you need to explain your own wrong statements.
Then please see your source code with my amendments. I added the problems as comment.
// This is just a dumped function and not a minimum reproducible example
// All header files are messing
// Obviously "using namespace std;" was used that should NEVER be done
// The function should retrun an unsigned value, best size_t, because a count can never be negative
// Same for n, that is the size of an array. Can also never be negative
// C-sytle arrays should NEVER be used in C++. NEVER. Use std::vector or std::array instead
int countDifferentNumbers(int v[], int n)
{
int counter = 0; // Now in C++ we can use braced initialzation instead of assignement
for (int i = 0; i < n; ++i)
{
for (int j = i; j < n; ++j)
{
if (v[i] == v[j + 1]) // Accessing out of bounds element
{
cout << "match" << endl; // Now endl needed here. Can all be done in one cout statement in one line
counter++; // Always counting up the same counter for all kind of double numbers.
cout << v[i] << endl;
}
}
}
return counter;
That was one point of the answer. But now the second point. Evene more important. The algorithm or the design is wrong. And finding the correct solution, this thinking before codingt, you need to do, before you write any line of code.
You obviously want to find the count of unique numbers in an array.
Then you could look what is already there on Stackoverflow. You would probaly find 20 answers already that coud give you a hint.
You could use std::unique. Please see here for a description. This function sounds like it does what you want, right? Some example implementation:
#include <iostream>
#include <unordered_map>
#include <vector>
#include <algorithm>
// If you want to keep the original data, remove the reference-specifier &
size_t countDifferentNumbers(std::vector<int>& v) {
std::sort(v.begin(), v.end()); // Sorting is precondition for std::unique
v.erase(std::unique(v.begin(), v.end()), v.end()); // Erase all non-unique elements
return v.size(); // Return the result
}
int main() {
std::vector test{ 1, 5, 5, 8, 1, 1 }; // Some test data
std::cout << countDifferentNumbers(test) << '\n'; // SHow result to user
return 0;
}
Then, we could count the occurence of each number in a std::map or std::unordered_map. And the number of counters will be the result. Example:
#include <iostream>
#include <unordered_map>
#include <vector>
#include <algorithm>
// If you want to keep the original data, remove the reference-specifier &
size_t countDifferentNumbers(std::vector<int>& v) {
std::unordered_map<int, size_t> counter{}; // Here we will count all occurences of different numbers
for (const int i : v) counter[i]++; // Iterate over vector and count different numbers
return counter.size(); // Count of different numbers
}
int main() {
std::vector test{ 1, 5, 5, 8, 1, 1 }; // Some test data
std::cout << countDifferentNumbers(test) << '\n'; // Show result to user
return 0;
}
But, then, thinking further, about what conatiners we could use, we will find out the answer from Igor Tandetnik. There are 2 containers that can hold unique values only. No double values. And these are: std::set and std::unordered_set., So, we can simply copy the data into one of those containers, and, only unique values will be stored there.
There are many ways to get the data into a set. But the simplest one is to use its range constructor. Then, we have unique elements, and, the containers size function will give the result:
See here: Constructor Number 2.
The result will be a function with one line like this
#include <iostream>
#include <unordered_set>
#include <vector>
// If you want to keep the original data, remove the reference-specifier &
size_t countDifferentNumbers(std::vector<int>& v) {
return std::unordered_set<int>(v.begin(), v.end()).size();
}
int main() {
std::vector test{ 1, 5, 5, 8, 1, 1 }; // Some test data
std::cout << countDifferentNumbers(test) << '\n'; // Show result to user
return 0;
}
And since functions with one line are often not so usefull, we can also write the final solution:
#include <iostream>
#include <unordered_set>
#include <vector>
int main() {
std::vector test{ 1, 5, 5, 8, 1, 1 }; // Some test data
std::cout << std::unordered_set<int>(test.begin(), test.end()).size() << '\n'; // Show result to user
return 0;
}
So, by analyzing the problem and choosing the right algorithm and container and using C++, we come to the most easy solution.
Please enable C++17 for your compiler.
first sort the array v. if n >0 then initially there must be one number which is unique so just increment the value of counter once. then with loop check if the two consecutive number are same or not. if same do nothing else increment the value of counter.
if you are writing code in c then use qsort. #include <stdlib.h> add this in header and. use qsort() func
here is the code:
#include <bits/stdc++.h>
using namespace std;
int countDifferentNumbers(int v[] , int n)
{
int counter = 0;
sort(v, v+ n); // if you are writing code in c then just write a decent sort algorithm.
if (n>0 ){
printf("%d\n", v[0]);
counter ++;
}
for(int i = 0; i < n-1; ++i)
{
if(v[i] == v[i+1]){
continue;
} else {
printf("%d\n", v[i+1]);
counter++;
}
}
return counter;
}
int main()
{
int v[] = {1, 5, 5, 8, 1, 1};
int result = countDifferentNumbers(v,6);
printf("unique number %d", result );
return 0;
}

Printing an array in reverse

Task
You'll be given an array of N integers and you have to print the integers in the reverse order.
Constraints
1<=N<=1000
1<=A_i<=10000, where A_i is the ith integer in the array.
Input
4
1 2 3 4
Output
4 3 2 1
#include <cmath>
#include <cstdio>
#include <vector>
#include <iostream>
#include <algorithm>
using namespace std;
int main() {
int N, y; //declaring N as the length of array
cin >> N; //intakes the length as an input
if (N>=1 && N<=1000){ //checks whether the length satisfies the rules
int a[N]; // makes an array containing N elements
for (int x =1; x<N; x++){ //starts transcription on the array
cin>>y; //temporarily assigns the input on a variable
if (y>=1&&y<=10000){ //checks if the input meets rules
a[x]=y; //copies the variable on the array
}
}
for (int z = N; z>1; z--){ //runs a loop to print in reverse
cout<<a[z]<<endl;
}
}
return 0;
}
Problem
Obtained output is
-1249504352
3
2
Indicating an error in transcription.
Question
Can somebody please tell me where I am making a mistake? Secondly, is it possible to directly check whether an input is meeting requirement rather than temporarily declaring a variable for it?
Here is a solution in idiomatic c++11, using std::vector, which is a dynamically resizable container useful for applications like this.
#include <vector>
#include <iostream>
#include <algorithm>
int main() {
int size;
std::cin >> size; // take in the length as an input
// check that the input satisfies the requirements,
// use the return code to indicate a problem
if (size < 1 || size > 1000) return 1;
std::vector<int> numbers; // initialise a vector to hold the 'array'
numbers.reserve(size); // reserve space for all the inputs
for (int i = 0; i < size; i++) {
int num;
std::cin >> num; // take in the next number as an input
if (num < 1 || num > 10000) return 1;
numbers.push_back(num);
}
std::reverse(numbers.begin(), numbers.end()); // reverse the vector
// print each number in the vector
for (auto &num : numbers) {
std::cout << num << "\n";
}
return 0;
}
A few things to note:
using namespace std is considered bad practice most of the time. Use (e.g.) std::cin instead for things which come from the std namespace.
numbers.reserve(size) is not necessary for correctness, but will make the program faster by reserving space in advance.
for ( auto &num : numbers ) uses a range-based for loop, available in c++11 and later versions.
You could make your for loop indices go from high to low:
for (int i = N-1; i > 0; --i)
{
std::cout << a[i] << "\n"; // Replace '\n' with space for horizontal printing.
}
std::cout << "\n";
This would apply with std::vector as well.
With std::vector, you can use a reverse iterator. There are other techniques available (as in other answers).

Party Invitation

The problem that I am working on right now is here, but I am of course not looking for the complete answer to this homework problem. All I am asking for is the steps in the final parts of the question. This is what I have so far:
int main()
{
cout << "Please enter the number of guests attending your party: ";
int k;
cin >> k;
cout << "Please enter the number of rounds of removal you'd like to perform: ";
int m;
cin >> m;
for (int i = 1; i <= m; i++) {
cout << "Please enter the multiple at which you'd like the removal to be at for round " << i << ": ";
int r;
cin >> r;
if (k % r == 0) {
k - r;
}
cout << k << endl;
}
system("pause");
}
This is all so confusing to me, and I truly have no idea where to turn to get answers. It seems like I'd need an array to solve this, but arrays in C++ cannot be variable, and the array length would be k, a variable input. Any help would be very appreciated.
I've read that question. you need a dynamic list like Linked list because you need to put and remove different items from different index so using arrays will be difficult.
Try to use std::vector or std::list, you can add or remove any any of list
#include <list>
std::list<int> mylist;
How can you add and remove values from list, check this link http://en.cppreference.com/w/cpp/container/list
For using your own Linklist, check this link How could i create a list in c++?
According to your question an std::vector will be the best choice because it is a combination of an array & linked list in raw terms or we can simply say it's a dynamic array.
However as you mentioned n your comment that you haven't been taught anything other than basic arrays & want a solution within whatever you have learnt, then you have to take an array. Now the problem is that arrays are static & you cannot delete elements from it. So all you can do is to keep a counter that will take care of the number of elements in it.
// array insert and delete
#include <iostream>
using namespace std;
void see_array (int a[], int f, int b)
{
for (int i=f; i<b; ++i)
cout << a[i] << ' ';
cout << '\n';
}
int get_pos (int a[], int f, int b, int num)
{
for (int i=f; i<b; ++i)
{
if (a[i] == num)
return i;
}
return -1; // if search is unsuccessful
}
int main()
{
int a[] = {1,2,3,4,5,6,7,8,9,10};
int front = 0, back = 10; // as we have 10 elements
// delete last element
--back;
see_array(a, front, back);
// delete first element
++front;
see_array(a, front, back);
// delete element from middle say 6
int pos = get_pos(a, front, back, 6);
if (pos != -1)
{
for (int i = pos; i<back; ++i) // shift elements towards left
{
a[i] = a[i+1];
}
--back; // decrease size of the array
see_array(a, front, back);
}
return 0;
}
/* Output :-
1 2 3 4 5 6 7 8 9
2 3 4 5 6 7 8 9
2 3 4 5 7 8 9
*/
I hope the above program is of some help to you !!! Good luck !!!

Sorting array and saving the old index in C++

I am doing online challenge which has to do the following.
There is a contest going in a village. So in the first line input two numbers N (which is how many people will join the contest) and K (how many of them can go to stage 2).
After that, we input N times the votes for each candidate in both stages.
Example input:
5 3
9 2
3 10
5 6
8 4
6 5
As you can see, we input N=5, K=3, which means 5 candidates, so 5 additional lines and 3 of them which go to stage 2.
After we sort the array the candidates with most votes are the ones with 6, 8 and 9. So they're going to stage 2. The winner is the one who has most votes in the stage 2 of them. In this case, 6 has 5 votes which is the most (8 has 4 and 9 has 2) and therefore we output the index of the 6 which is 5.
What I got so far:
#include <iostream>
#include <algorithm>
using namespace std;
int main()
{
int arr[50],nizabackup[50],n,k,niza2[50],saveindex[50],indexp=0;
cin >> n >> k;
for(int i=0;i<n;i++)
{
cin >> arr[i] >> niza2[i];
nizabackup[i] = arr[i];
}
sort(arr,arr+n);
for(int j=n;j>=k;j--)
{
for(int k=0;k<n;k++)
{
if(arr[j]==nizabackup[k])
{
saveindex[0]=k;
indexp++;
}
}
}
sort(saveindex,saveindex+indexp);
cout << saveindex[indexp];
return 0;
}
I need a hint what to do and also additional question -- why my debugger doesn't read the second for loop?
OK, alternative implementation. There's more set-up, but read main first and see how much simpler the actual logic is.
#include <vector>
#include <iostream>
#include <algorithm>
struct Contestant {
int index;
int firstVote;
int secondVote;
Contestant(int i, int v1, int v2) : index(i), firstVote(v1), secondVote(v2)
{}
};
// return true if l should come before r in sorted result
bool byFirstVote(Contestant const &l, Contestant const &r) {
return l.firstVote > r.firstVote; // sort by first vote
}
bool bySecondVote(Contestant const &l, Contestant const &r) {
return l.secondVote > r.secondVote; // sort by second vote
}
int main()
{
int n, k;
std::cin >> n >> k;
// populate a single vector of {index, firstVote, secondVote}
std::vector<Contestant> contestants;
for(int i=0; i<n; i++) {
int v1, v2;
std::cin >> v1 >> v2;
contestants.push_back(Contestant(i+1, v1, v2));
}
// sort all by firstVote, then sort first k by secondVote
std::sort(contestants.begin(), contestants.end(), byFirstVote);
std::sort(contestants.begin(), contestants.begin()+k, bySecondVote);
std::cout << contestants.front().index << std::endl;
}
I'm storing the index (starting from 1, not zero, as per your example), and both votes, all together in a single structure.
Then, I just change which field I sort on.