Beginner programmer here can someone please explain to me how this loop works.
How can the loop detect the duplicate element in the array?
sorry for the simple question.
#include <iostream>
using namespace std;
int main()
{
int num[5];
int numSize = sizeof(num) / sizeof(num[0]);
for(int i = 0; i < numSize; i++)
{
cout << "Enter number : ";
cin >> num[i];
if(i >= 0)
{
for(int j = 0 ; j < numSize; j++)
{
if(num[i] == num[j] && (i != j))
{
i--;
j++;
}
}
}
}
for(int p = 0; p < numSize; p++)
cout << num[p] << " ";
}
Avoid indexing when it is possible. It is not final solution but it may show you right direction.
#include <iostream>
#include <algorithm>
int main()
{
int num[] = { 0, 5, 6, 8, 0, 2, 5, 8 };
std::sort(std::begin(num), std::end(num));
auto it = std::begin(num);
while(1) {
it = std::adjacent_find(it, std::end(num));
if(it != std::end(num)) {
std::cout << "Double pairs " << *it << " and " << *(it+1) << std::endl;
++it;
}
else {
break;
}
}
return 0;
}
Output:
Double pairs 0 and 0
Double pairs 5 and 5
Double pairs 8 and 8
Related
The problem is to find if a given sequence of numbers can form a valid permutation or not. The problem statement is trivial for the real problem. So, I am pushing a pair of integers into the vector. The first part being the number itself and second being 0 or 1.
The code works fine till a sequence 1041 long (specific after debugging a lot). Just to debug I added a print statement after pushing each pair inside the vector. For a length of 1042, the code shows pushed 1040 and then pushed 1 (which is weird) and then just hangs on there.
I am attaching the code as well as the input and terminal output.
You can just check the main function
Code
#include <iostream>
#include <vector>
#include <algorithm>
#include <chrono>
using namespace std;
bool comparator_function(pair<int, int> a, pair<int, int> b) {
return (a.first < b.first);
}
//index_added -> the index at which the latest element was added
void set_r_array(int* r_array_ref, int* per_array_ref, int size, int* count, int index_added) {
for(int i = 1;i <= size; i++) {
count[i] = 0;
}
int temp = index_added;
while(index_added <= size) {
if(index_added == size) {
if(per_array_ref[index_added] == 0) {
r_array_ref[temp] = size;
break;
}
else {
r_array_ref[temp] = -1;
break;
}
}
else {
if(per_array_ref[index_added] == 0) {
r_array_ref[temp] = index_added;
break;
}
else {
index_added++;
}
}
}
for(int i = 1;i <= size; i++) {
if(r_array_ref[i] != -1) {
count[r_array_ref[i]]++;
}
}
}
bool check_max(int* count, int next_element, int size) {
int max_count = -1, index = 0;
for(int i = 1;i <= size; i++) {
int temp_val = count[i];
if(max_count <= temp_val) {
max_count = temp_val;
index = i;
}
}
int num = 0;
for(int i = 1;i <= size; i++) {
if(count[i] == max_count) {
num++;
}
}
//one max
if(num == 1) {
if(next_element == index) {
return true;
}
return false;
}
else {
for(int i = 1;i <= size; i++) {
if(count[i] == max_count) {
if(next_element == i) {
return true;
}
}
}
return false;
}
}
int main() {
int testCases;
cin >> testCases;
cin.ignore();
while(testCases-- > 0) {
int n, result_flag = 0;
cin >> n;
cin.ignore();
vector<pair<int, int>> per;
int temp;
for(int i = 0;i < n; i++) {
cin >> temp;
pair<int, int> temp_pair = make_pair(temp, i+1);
per.push_back(temp_pair);
//debug statement
cout << "pushed " << temp << endl;
}
auto start = std::chrono::high_resolution_clock::now();
cout << "start" << endl;
sort(per.begin(), per.end(), comparator_function);
int permutation_array[n+1], r_array[n+1], count[n+1];
for(int i = 0;i <= n; i++) {
permutation_array[i] = 0;
r_array[i] = i;
count[i] = 1;
}
cout << "end" << endl;
permutation_array[per[0].second] = per[0].first;
set_r_array(r_array, permutation_array, n, count, per[0].second);
//insertion of numbers
for(int i = 1;i < n; i++) {
//check if the next element inserted has the largest count rn or not
int next_element = per[i].second;
if(!check_max(count, next_element, n)) {
cout << "No" << endl;
result_flag = -1;
break;
}
permutation_array[per[i].second] = per[i].first;
set_r_array(r_array, permutation_array, n, count, per[i].second);
}
if(result_flag == 0) {
cout << "Yes" << endl;
}
auto stop = std::chrono::high_resolution_clock::now();
auto duration = std::chrono::duration_cast<std::chrono::microseconds>(stop - start);
cout << "Time: " << duration.count() << " microseconds" << endl;
}
}
Input 1
1
5
2 3 4 5 1
Output 1
pushed 2
pushed 3
pushed 4
pushed 5
pushed 1
start
end
Yes
Input 2
1
1042
1 2 3 4 ... so on till 1042
Output 2
pushed 1
pushed 2
.
.
.
pushed 1040
pushed 1
and then hangs, from here on
The complexity of the code is O(n^2). So, I don't think it has to do anything with that. Since the input can be at max 10^4 order. Moreover, according to the print debugging, I think the issue is with the input.
You have issue with input as you reach console line limit.
Put your input into a file should solve that issue.
Then you should be able to debug your algorithm which seems more complicated than needed.
I have a row of ten numbers for example:
5 5 6 7 5 9 4 2 2 7
Now I want a program that finds all duplicates and gives them out in the console like 3 times 5, 2 times 2, 2 times 7.
While I did code an algorithm that finds duplicates in a row of numbers I can't give them out in the console as described. My program will output:
3 times 5
2 times 5
2 times 7
2 times 2
How can I solve this problem?
#include <iostream>
using namespace std;
int main()
{
int arr[10];
int i,j;
int z = 1;
for(i = 0; i < 10; i++) {
cin >> arr[i];
}
for(i = 0; i < 10; i++){
for(j = i+1; j < 10; j++){
if(arr[i] == arr[j]){
z++;
}
}
if(z >= 2){
cout << z << " times " << arr[i] << endl;
z = 1;
}
}
return 0;
}
You can use the STL here (C++11):
int arr[10];
std::map<int, int> counters;
for (auto item : arr)
{
cin >> item;
++counters[item];
}
std::for_each(counters.begin(), counters.end(), [](const std::pair<int,int>& item)
{
if(item.second > 1) std::cout << item.second << " times " << item.first << std::endl;
});
You need to check that arr[i] is not already found before, like this for example:
if(z >= 2) {
int found_before = 0;
for(j = 0; j < i; ++j)
if(arr[i] == arr[j])
found_before = 1;
if(!found_before)
cout << z << " times " << arr[i] << endl;
z = 1;
}
which will print:
3 times 5
2 times 7
2 times 2
That way you don't print 5 again.
With your code it would print that it found 5 three times (for the first 5 in your array), and then when it would move to he second 5 in your array, it would forgot about the first 5 in your array, and report that it found 5 twice (itself and the 5th number of the array).
Why not use STL?
std::map<int, int> counter;
for (i = 0; i < 10; i++)
counter[arr[i]] ++;
for (i = 0; i < 10; i++) {
if (counter.count(arr[i]) > 0){
std::cout << counter[arr[i]] << " times "<< arr[i] << std::endl;
counter.erase(arr[i]);
}
}
std::map is a convenient tool for this job. You can easily count up occurrences of a specific number. After counting, you can print the count of each array element. With counter.erase, it's guaranteed that you won't print the same element for multiple times.
Why keeping your algorithm idea, I suggest to create sub method:
std::size_t count(const int* arr, std::size_t start, std::size_t end, int value)
{
std::size_t res = 0;
for (std::size_t i = start; i != end; ++i) {
if (arr[i] == value) {
++res;
}
}
return res;
}
then your fixed algorithm would be:
for (std::size_t i = 0; i != 10; ++i) {
if (count(arr, 0, i, arr[i]) != 0) {
continue; // Already visited
}
auto total = count(arr, i, 10, arr[i]);
if(total >= 2){
std::cout << z << " times " << arr[i] << std::endl;
}
}
An easy way is to make another array for it, especially if the numbers are not that big.
Lets say you have initialized your array like so: int nums[10] = { 5, 5, 6, 7, 5, 9, 4, 2, 2, 7 }
int result[max(nums)]; //Fill with zeroes, max(nums) is the highest number in the array
for(int i = 0; i < 10; i++) {
result[nums[i]]++;
}
for(int i = 0; i < max(nums); i++) {
if (result[i] > 1) cout << result[i];
}
Mind you this isn't optimized for memory. For larger number contents you might want to consider hashmaps.
If you don't need performance but rather compact code, then std::multiset with std::upper_bound is an alternative:
#include<set>
#include<iostream>
#include<algorithm>
int main(int a, char** b)
{
int array[] = {5, 5, 6, 7, 5, 9, 4, 2, 2, 7};
std::multiset<int> a(std::begin(array), std::end(array));
for(auto it = a.begin(); it != a.end(); it = std::upper_bound(a.begin(), a.end(), *it))
{
if(a.count(*it) > 1)
std::cout << *it << " times " << a.count(*it) << std::endl;
}
return 0;
}
I have to create a code where the user inputs a number which is a perfect square, and I have to show its root. I've made this code, but I'm getting Segmentation Fault 11 , in this piece: int j = squareRootVector[i];
squareRoot.push_back(j);.
I can't change the code too much, so is there a way that I can do that?
#include <iostream>
#include <vector>
using namespace std;
int main() {
cout <<
"Enter the number:\n";
int input;
int number = input;
int divider = 2;
vector<int> squareRootVector;
vector<int> squareRoot;
cin >> number;
for(int divider = 2; number > 1; divider++) {
while((number % divider) == 0) {
number /= divider;
cout << number << endl;
squareRootVector.push_back(divider);
}
}
for(int i = 0; i < squareRootVector.size(); i++) {
cout << squareRootVector[i] << " ";
/*******PROBLEM*******/
if(squareRootVector[i] == squareRootVector[i+1]) {
int j = squareRootVector[i];
squareRoot.push_back(j);
}
/*********************/
}
int root;
for (int i = 0; squareRoot.size(); i++) {
root = root * squareRoot[i];
}
cout << "Square Root of " << input << " is: " << root << endl;
return 0;
}
The behaviour on accessing squareRootVector[i+1] with i just one below size (which your loop constaint allows) is undefined.
Consider writing
for (std::size_t i = 1; i < squareRootVector.size(); i++) {
instead, and rebasing the for loop body accordingly. I've also slipped in a change of type for i.
Shortly, the problem is that the last cycle in the last "for":
for(int i = 0; i < squareRootVector.size(); i++)
has the following line in it:
squareRootVector[i] == squareRootVector[i+1];
This is an "out of limits" error: squareRootVector only has squareRootVector.size() elements (let's say n), and the elements are indexed from 0 to n-1.
squareRootVector[i+1] in the last cycle points one element after the last one of squareRootVector, which is undefined behavior.
Using vector::iterator is proper way.
for(vector<int>::iterator it = squareRootVector.begin(); it != squareRootVector.end(); ++it)
{
if( (it+1) == squareRootVector.end() )
{
//what to do if there's no next member???
break;
}
if( *it == *(it+1) )
{
squareRoot.push_back(*it);
}
}
Thanks for the answers, guys. I've ended up with this code:
#include <iostream>
#include <vector>
using namespace std;
int main() {
cout << "Enter the number:\n";
int input = 0;
int number = 0;
cin >> input;
number = input;
int divider = 2;
vector<int> squareRootVector;
vector<int> squareRoot;
for(int divider = 2; number > 1; divider++) {
while((number % divider) == 0) {
number /= divider;
squareRootVector.push_back(divider);
}
}
int vectorSize = squareRootVector.size() - 1;
for(int i = 0; i < vectorSize; i++) {
if(squareRootVector[i] == squareRootVector[i+1]) {
int j = squareRootVector[i];
squareRoot.push_back(j);
}
}
int root = 1;
for (int i = 0; i < squareRoot.size(); i++) {
root = root * squareRoot[i];
}
cout << "Square Root of " << input << " is " << root << endl;
return 0;
}
Say I have an array of 4 different numbers.
int numbers[4] = {50234, 50356, 50454, 50934};
How do you make a nested for loop in C++ to sort through these numbers from back to front in order to identify the required amount of digits needed for uniqueness?
From the example you can tell that you'll need 3 digits from the back to make sure no numbers contain similar tails of numbers. 50234, 50934 = 3 digits to have them unique = 502 and 509 respectively.
What would the for loop look like to go through each of these numbers one by one, number by number, and sort out identical numbers to reach an output of 3?
It would go like this:
4
6 - discard this number, it's not identical
4
4
Then:
3
5 - discard this number
3
Then:
2
9 Hurray! No similar numbers anymore, print out 3 being the answer.
I'm stumped and can't figure it out.
Any help would be greatly appreciated, thank you.
Say you start with
#include <unordered_set>
#include <iostream>
#include <vector>
#include <algorithm>
int main() {
const std::vector<int> numbers{50234, 50356, 50454, 50934};
You can transform it into a vector of strings:
std::vector<std::string> string_numbers;
std::for_each(std::begin(numbers), std::end(numbers), [&](int n){ string_numbers.push_back(std::to_string(n)); });
Now we'll check the number of digits required, starting at 1:
size_t digits = 1;
while(true) {
At each iteration, we'll create an unordered_set
std::unordered_set<std::string> partials;
For each number, we'll attempt to place digits digits of it into the set:
for(const auto &s: string_numbers) {
if(s.size() <= digits) {
std::cout << "not unique" << std::endl;
return 0;
}
partials.insert(s.substr(0, digits));
}
If the size of the set is the size of the vector, we're done:
if(partials.size() == numbers.size()) {
std::cout << digits << " required" << std::endl;
return 0;
}
Otherwise, we need to increase the number of digits:
++digits;
}
}
Full code:
#include <unordered_set>
#include <iostream>
#include <vector>
#include <algorithm>
int main() {
const std::vector<int> numbers{50234, 50356, 50454, 50934};
std::vector<std::string> string_numbers;
std::for_each(std::begin(numbers), std::end(numbers), [&](int n){ string_numbers.push_back(std::to_string(n)); });
size_t digits = 1;
while(true) {
std::unordered_set<std::string> partials;
for(const auto &s: string_numbers) {
if(s.size() <= digits) {
std::cout << "not unique" << std::endl;
return 0;
}
partials.insert(s.substr(0, digits));
}
if(partials.size() == numbers.size()) {
std::cout << digits << " required" << std::endl;
return 0;
}
++digits;
}
}
if you want to sort numbers so use one of sort algorithms let's say bubble sort. then check for uniqueness and store the unique values in a new array then print them:
we make our code for understanding and practice but in a real program we use libraries they are too much powerful and quick:
#include <iostream>
using std::cout;
using std::endl;
int main()
{
int numbers[4] = {50234, 50356, 50454, 50934};
// int numbers[4] = {50234, 50356, 50454, 50356};
for(int i(0); i < 4; i++)
{
for(int j(i + 1); j < 4; j++)
{
if(numbers[i] > numbers[j])
{
numbers[i] ^= numbers[j];
numbers[j] ^= numbers[i];
numbers[i] ^= numbers[j];
}
}
}
for(int i = 0; i < 4; i++)
cout << numbers[i] << ", ";
int nUniq = 0;
bool isUniq = true;
for(int i = 0; i < 4; i++)
{
isUniq = true;
for(int j(i + 1); j < 4; j++)
{
if(numbers[i] == numbers[j])
{
isUniq = false;
break;
}
}
if(isUniq)
nUniq++;
}
cout << nUniq << endl;
int* ptrUniq = new int[nUniq];
int k = 0;
for(int i = 0; i < 4; i++)
{
isUniq = true;
for(int j(i + 1); j < 4; j++)
{
if(numbers[i] == numbers[j])
{
isUniq = false;
break;
}
}
if(isUniq)
{
ptrUniq[k] = numbers[i];
k++;
}
}
cout << "\nhere are uniq values:\n\n";
for(int i = 0; i < nUniq; i++)
cout << ptrUniq[i] << ", ";
delete[] ptrUniq;
ptrUniq = NULL;
cout << endl << endl;
return 0;
}
This question already has answers here:
Bitset in C++, about continuously add
(2 answers)
Closed 8 years ago.
I'm trying to create a loop that changes the values in a boolean array so that it looks like the array is incrementing in binary values.
For example
1st iteration [0|0|0]
2nd iteration [0|0|1]
3rd iteration [0|1|0]
4th iteration [0|1|1]
etc.
This array is dynamic, however, and can be different sizes. So whatever loop I write would need to also work on an array with five elements instead of three.
Apologies for not having any starting code, but I've been frustrating myself with this for hours and still can't even come up with how to begin.
Try this. This may not be complete but you could do something similar
#include <iostream>
using namespace std;
void increment(bool* array, int len)
{
for (int i = len - 1; i >= 0; --i)
{
if ( ! array[i])
{
array[i] = true;
return;
}
array[i] = false;
}
}
int main()
{
bool* array = new bool[10];
for (int i = 0; i < 5; ++i)
{
increment(array, 10);
for (int i = 0; i < 10; ++i)
{
cout << (array[i] ? 1 : 0) << "|";
}
cout << endl;
}
return 0;
}
#include <iostream>
#include <cmath>
#include <memory>
using namespace std;
void ArrayIterate(int);
void printArray(bool*,int);
void ArrayIterate(int arraySize)
{
int decimal_value = 0;
int decimal_place_value = 0;
bool* boolArray = new bool(arraySize);
long double max_itr = pow(2,arraySize);
for (int i = 0; i < max_itr ; ++i)
{
decimal_value = i;
// set array values
for ( int k = arraySize - 1; k >= 0; --k)
{
decimal_place_value = pow(2,k);
if( decimal_value != 0 && decimal_value / decimal_place_value >= 1 )
{
boolArray[k] = true;
decimal_value -= decimal_place_value;
}
else
boolArray[k] = false;
}
printArray(boolArray,arraySize);
cout << " = " << i << endl; ;
}
delete boolArray;
return;
}
void printArray(bool* boolArray, int arraySize)
{
cout << "\t";
for(int i = arraySize - 1; i >= 0; --i)
cout << ((boolArray[i] == true)? 1 : 0) << " ";
return;
}
int main()
{
cout << "\n\n";
ArrayIterate(4);
cout << "\n\n" << endl;
return 0;
}