I'm trying to solve CSES Problem Set: Apartments, which have input like this in 3 lines, but I am unable to process/pass all three lines in the Windows terminal. I am using Geany editor and compilation is successful.
10 10 0
37 62 56 69 34 46 10 86 16 49
50 95 47 43 9 62 83 71 71 7
Can anyone review and tell me what is wrong? Is there fault in my logic?
#include <bits/stdc++.h>
using namespace std;
int n, m, k;
int main()
{
vector<int> v1;
vector<int> v2;
vector<bool> allotted(n, false);
cin >> n >> m >> k;
for (int i = 0; i < n; ++i) {
cin >> v1[i];
}
for (int j = 0; j < m; ++j) {
cin >> v2[j];
}
sort(v2.begin(), v2.end());
sort(v1.begin(), v1.end());
int ans = 0;
for (int req = 0; req < n; ++req) {
for (int x = -k; x <= k; ++x) {
if (find(v2.begin(), v2.end(), v1[req]+x) != v2.end() && alloted[req] == false) {
++ans;
allotted[req] = 1;
}
else {
continue;
}
}
}
cout << ans;
return 0;
}
Output:
10 10 0
37 62 56 69 34 46 10 86 16 49
------------------
(program exited with code: -1073741819)
You must allocate elements before accessing them or add elements via push_back.
To allocate elements, using resize() is one good way.
vector<int> v1;
vector<int> v2;
vector<bool> allotted(n, false); // note that n is zero here!
cin>>n>>m>>k; // after here, the size will be n (may not when the reading fails)
// allocate elements
v1.resize(n);
v2.resize(m);
allotted.resize(n);
You forgot to tell your vectors how long they should be. As a result you 're reading data into non-existing variables.
As an alternative to MikeCAT's answer, if you delay the declaration of your vectors until you know how big they need to be then you can create them at the correct size.
cin>>n>>m>>k;
vector<int> v1(n); // v1 has size n
vector<int> v2(m); // v2 has size m
vector<bool> allotted(n, false); // allotted has size n
Related
I want to sort using the "Bubble Sort" algorithm of the 2d array. My array size will be about array[100000][100000]. my input number will be n=100,000.
For now we can use a small size of the array to fix the sorting issue.
I need to sort them in descending order for the first number(first number's line).
If the first number of 2 values are the same, then I have to sort them according to their second number.
Finally I have to output the result into a txt file
Let's' understand using an example. Here, my input looks like this
41 11
34 4
69 4
78 6
62 8
5 5
81 3
5 10
above our input example and we have a couple of inputs. Now I need to sort them descending orders for the first number. But if the first number of 2 values are the same, then sort them according to their second number.
Example output below,
81 3
78 6
69 4
62 8
41 4
34 4
5 10
5 5
If anyone can please help me.
I am a beginner so I am trying to input the file manually to solve this sorting problem. I can solve the sorting problem then I will try to input and out the text.
Something I have tried but not worked. I am still trying to solve it.
#include<bits/stdc++.h>
#include <algorithm>
using namespace std;
int main ()
{
int arr[100][100];
int n,j;
cin >>n;
cout << "Please enter a number: " << endl;
for(int i=0;i<n;i++)
{ for (int j=i; j<n; j++)
{
cin>>arr[i][j];
}
}
cout << "Unsorted array:" << endl;
for (int i=0; i<n; i++)
{
for (int j=i; j<n; j++)
{
cout<<arr[i][j]<<"\t";
}
}
for (int i=0; i<=n; i++)
{
for (int j=i+1; j<=n-1; j++)
{
int temp;
if(arr[i]>arr[j])
{
temp=arr[i];
arr[i]=arr[j];
arr[j]=temp;
}
}
}
return 0;
}
Use a std::vector<std::array<int,2>>for your base container. The dynamic growth capabilities of std::vector solves your stack space issue, and the std::array use gives you tied cell comparison. I.e. you can do this:
std::array<int, 2> ar1{1,2}, ar2{1,3};
if (ar1 < ar2) ...
and it will do the right thing. The result then boils down to effectively this:
#include <iostream>
#include <array>
#include <vector>
#include <utility>
int main()
{
std::vector< std::array<int,2> > v;
std::size_t n;
if (std::cin >> n && n > 0)
{
std::array<int,2> row;
while (n-- && std::cin >> row[0] && std::cin >> row[1])
v.emplace_back(row);
// bubblesort the content
std::size_t len = v.size();
while (len-- > 0)
{
bool swapped = false;
for (std::size_t i=0; i<len; ++i)
{
// std::array support multi-cell comparison.
if (v[i] < v[i+1])
{
// use library swap to swap entire row.
std::swap(v[i], v[i+1]);
swapped = true;
}
}
// early exit if no swaps happened on the last pass
if (!swapped)
break;
}
// report final output.
for (auto const& row : v)
std::cout << row[0] << ' ' << row[1] << '\n';
}
}
Input
8
41 11
34 4
69 4
78 6
62 8
5 5
81 3
5 10
Output
81 3
78 6
69 4
62 8
41 11
34 4
5 10
5 5
I was trying this problem - Minimum Cost Path.
I have solved the problem using Dijkstra's Shortest Path Algorithm. But when i tried this using recursion+memoisation i.e. using dynamic programming, i got stuck and could not debug my code. I need help as to where my code is wrong!!
I am really glad for the help.
#include<bits/stdc++.h>
using namespace std;
int n;
int a[105][105], dp[105][105];
int dfs(int x, int y){
if(x < 0 || y < 0 || x >= n || y >= n){
return INT_MAX;
}
if(x == 0 && y== 0){
return a[0][0];
}
if(dp[x][y] != -1){
return dp[x][y];
}
dp[x][y] = a[x][y] + min(dfs(x-1, y), min(dfs(x, y-1), min(dfs(x+1, y), dfs(x, y+1))));
return dp[x][y];
}
int main(){
int tt;
cin >> tt;
while(tt--){
int n;
cin >> n;
for(int i = 0 ; i < n; i++){
for(int j = 0; j < n; j++){
cin >> a[i][j];
dp[i][j] = -1;
}
}
cout << dfs(n-1, n-1) << endl;
}
return 0;
}
Example:
Input:
2
5
31 100 65 12 18 10 13 47 157 6 100 113 174 11 33 88 124 41 20 140 99 32 111 41 20
2
42 93 7 14
Output:
327
63
I am getting 2147483647 as the output for both the cases, which is the value of INT_MAX.
The global variable n that dfs looks at is always zero (by static initialization), it's never assigned a value. When main calls, say, dfs(4, 4), the function immediately returns INT_MAX due to 4 >= 0 check.
Once you fix this simple issue, you'll discover that your program crashes due to stack overflow. You see, dfs(4, 4) calls dfs(3, 4), which in turn calls dfs(4, 4), which calls dfs(3, 4), which ...
This is not really a dynamic programming problem. It's a "shortest path in a graph" problem, suitable for, say, Dijkstra or A* algorithms.
I'm trying to create an array of pointers to a 2D (5 X 12) array in C++.
The ptr array has 5 elements. Each element should hold the address of the 1st element of the respective row of the 2D array. So 1st element should point to 1st element of 1st row, 2nd element should point to 1st element of 2nd row, and so on.
The 5th element of my array of pointers seems to point to a garbage value.
Code and output shown below. Can anyone please let me know why?
#include <iostream>
#include <cstdlib>
#include <iomanip>
using namespace std;
int main( )
{
int rainMatrix[5][12] = {{0}}; //declare and initialize rain matrix
int *matrix_ptr[5] = {NULL};//declare and initialize array of pointers
int **matrix_ptr_ptr = matrix_ptr;
for (int i = 0; i < 5; ++i)
matrix_ptr[i] = &rainMatrix[i][0];
rainGen(matrix_ptr_ptr, 5, 12); //generate a random matrix
//display the matrix
for (int i = 0; i < 5; ++i) {
for (int j = 0; j < 12; ++j) {
cout << setw(2) << rainMatrix[i][j] << " ";
}
cout << endl;
}
for (int i = 0; i < 5; ++i)
cout << setw(2) << *matrix_ptr[i] << " " << rainMatrix[i][0] << endl;
return 0;
}
void rainGen (int **pptr, int row, int col)
{
unsigned int seed = 43;
unsigned int rv;
srand(seed);
for (int i = 0; i < row; ++i) {
for (int j = 0; j < col; ++j) {
rv = rand() % 100;
**pptr = rv;
*pptr += 1;
}
pptr++;
}
}
OUTPUT
11 1
88 11
28 88
25 28
1477892712 25
You're manipulating the wrong pointer in the innermost loop. Consider the pointer arithmetic carefully:
pptr essentially points to matrix_ptr[0];
on the first iteration, the double indirection means **pptr will set what you want, but then
*pptr += 1 will modify the contents of matrix_ptr[0], which means it no longer points to the beginning of the matrix.
Subsequent passes through the loop compound the situation drastically.
Modifying pptr won't help because it actually points to the wrong thing: it points to matrix_ptr, so incrementing it merely once moves its address from that of matrix_ptr[0], which points to rainMatrix[0][0], to that of matrix_ptr[1], which points to rainMatrix[1][0]. That is the wrong address for the next entry of the matrix, which is rainMatrix[0][1]. In essence, you've moved to the next row, instead of to the next column.
Try this for the innermost loop instead:
for (int i = 0; i < row; ++i)
{
auto qptr = *pptr;
for (int j = 0; j < col; ++j)
{
rv = rand() % 100;
*qptr = rv;
qptr += 1;
}
pptr++;
}
}
In this case, qptr is given the address of the first entry in the matrix. *qptr = rv sets the value. qptr += 1 increments the position of qptr while leaving *pptr alone - and, by extension, it leaves matrix_ptr[0] alone.
John Perry correctly identified the problem, but you have several option to deal with it. You are incorrectly incrementing *pptr += 1 Beyond using auto, you can simply index the pointer with the offset of j, e.g.
*(*pptr + j) = rv;
or
(*pptr)[j] = rv;
Either will work. Putting it together in your rainGen function, you could do:
void rainGen (int **pptr, int row, int col)
{
unsigned int seed = 43;
unsigned int rv;
srand(seed);
for (int i = 0; i < row; ++i) {
for (int j = 0; j < col; ++j) {
rv = rand() % 100;
// *(*pptr + j) = rv; /* or */
(*pptr)[j] = rv;
}
pptr++;
}
}
(note: seed and srand(seed) should be moved to main() if there is the potential that rainGen could be called more than once -- srand should only be called once)
Example Use/Output
Both will produce the desired output:
$ ./bin/raingen
72 71 65 94 0 13 49 17 36 49 67 51
87 68 45 15 91 72 16 80 77 35 9 81
11 88 73 59 24 22 37 48 45 54 94 45
19 44 62 56 45 81 59 32 49 4 99 92
28 16 24 5 3 34 38 14 22 12 26 98
72 72
87 87
11 11
19 19
28 28
You are modifying the pointers in the pointer-array matrix_ptr within your rainGen function, so that all of them point past the end and further accesses go to "random" memory locations, which is undefined behavior. Tools like valgrind can find such errors.
Can somebody tell me what is the problem with this program?
The idea is to display "Yes" if the vector array satisfies all these criteria:
The array elements are not sorted in ascending order.
The array contains distinct elements.
All the array elements should have a value between 1 to n inclusive.
Otherwise "No".
The program aborts when it reaches the line at if(bSort).
Is there anything wrong with the iterator increment?
#include <iostream>
#include <string>
#include <bits/stdc++.h>
using namespace std;
std::string solve(vector <int> &a, int n) {
vector<int> visited (n);
int i=0;
for(std::vector<int>::iterator it = a.begin(); it != a.end(); ++it) {
i++;
if((it+1)!=a.end() && (*it > *(it+1)))
{
bSort = false;
}
if(std::find(visited.begin(), visited.end(), *it)!=visited.end())
{
return "No";
}
else
{
visited[i] = *it;
}
if(*it <= 0 || *it > n)
{
return "No";
}
}
if(bSort)
return "No";
else
return "Yes";
}
int main() {
int q;
cin >> q;
for(int a0 = 0; a0 < q; a0++){
int n;
cin >> n;
vector<int> a(n);
for(int a_i = 0; a_i < n; a_i++){
cin >> a[a_i];
}
std::string result = solve(a,n);
cout << result << endl;
}
return 0;
}
The issue appears to be happening only with the following input:
1
30
18 8 24 20 7 17 5 9 26 21 25 12 11 15 30 13 19 16 22 10 14 1 3 29 23 2 6 28 4 27
I'm not sure the problem has to do with iterators specifically.
At the very beginning of the loop, variable i is incremented before it's used, which means the set of numbers that i will range between is [1, vector.size()]. This means that at some point, you'll access vector[vector.size()], which is undefined behavior and can crash your program.
In your program specifically, given the input you provided, because none of the numbers in your example code are duplicated, the else branch of the std::find(...) conditional statement is always executed, which means you end up calling visited[30] at some point, which again, is out of bounds and undefined behavior, potentially causing a crash.
I'm trying to generate a 5x20 matrix filled with random numbers. How can I make sure none of the random numbers are duplicates? This is the code I have for filling the matrix with random numbers.
srand(time(0));
int matrix[5][20];
int i = 0;
int j = 0;
for (i = 0; i < 5; i++)
{
for (j = 0; j < 20; j++)
{
matrix[i][j] = 1 + (rand() % 100);
cout << matrix[i][j] <<"_";
}
cout << endl;
}
the code works but there are sometimes duplicates. If this were an array I could make use of a simple for loop and compare all of the elements in the array. but I have no idea how to do so with a matrix. I have searched everywhere but cant seem to find a solution.
It's not quite fit your question title but I think you should take a look.
for (i = 0; i < 5; i++)
{
for (j = 0; j < 20; j++)
{
matrix[i][j] = 1 + (rand() % 100);
cout << matrix[i][j] <<"_";
}
cout << endl;
}
I don't know the 5x20 and 100 (in rand() % 100) is compulsory or just an example you want to give. So I suggest for all case I can consider:
Let call the number of matrix elements is a, the number of set (contains all possible generated number) is b. In your is example, a is 5x20=100 and b is 100 (from 1 to 100).
a > b: no valid matrix without duplicates since Dirichlet principle
a == b: take a look at http://en.cppreference.com/w/cpp/algorithm/random_shuffle. Just create an 1-dimension array containing consecutive number from 0 to b-1 (or from min and max of your range) and permute them. Then use it to fill in the matrix.
a < b: similar to case a==b, but you just take a part of the permutation.
Of course, when a =< b then you can use rand() but you have to check duplicate and retry rand(), which is quite complicated. You can create a mark array (which cost memory) or iterate through your matrix again (which cost time).
as a heads up, you shouldn't use rand() unless you've got explicit reasons to (such as a professor's requirements).
The following approach uses a GetIndex function to simulate an int[5][20] with an int[100]. See if you can figure out how to use the code I wrote to create an int[5][20].
Your code fills the matrix with random numbers between 1 and 100 (1 + (rand() % 100)) inclusively, but you do no work to ensure you don't get duplicates! So you won't be able to guarantee that you don't get duplicates (in fact, it's very unusual for you to get no duplicates).
If you first initialize all your values to 1,...,100 and then later shuffle them, you know you have no duplicates.
#include <iostream>
#include <iomanip>
#include <random>
#include <algorithm>
constexpr size_t kDefaultMatrixHeight = 20;
constexpr size_t kDefaultMatrixWidth = 5;
constexpr size_t GetIndex(size_t i, size_t j) {
return i * kDefaultMatrixWidth + j;
}
int main() {
int matrix[kDefaultMatrixWidth * kDefaultMatrixHeight];
for (size_t i = 0 ; i < kDefaultMatrixHeight * kDefaultMatrixWidth ; i++) {
matrix[i] = i + 1;
}
std::mt19937 rng(std::random_device{}());
std::shuffle(std::begin(matrix), std::end(matrix), rng);
for (size_t i = 0 ; i < kDefaultMatrixHeight ; i++) {
for (size_t j = 0; j < kDefaultMatrixWidth ; j++) {
std::cout << std::setw(4) << matrix[GetIndex(i,j)];
}
std::cout << '\n';
}
}
And for example output:
Test#Test:/tmp/example$ g++ example.cpp && ./a.out
93 28 70 14 39
83 3 80 95 58
42 69 71 16 49
75 63 41 82 46
26 50 81 33 97
65 10 77 68 12
8 19 30 86 37
57 24 78 31 88
2 90 4 13 56
36 15 35 32 85
29 76 99 45 18
54 11 44 62 98
9 96 79 34 27
40 21 52 22 55
72 1 47 92 59
94 7 64 91 53
74 5 61 100 89
48 23 66 67 51
38 6 87 17 20
60 25 84 43 73
not exactly answer your question but for your purpose you can try something like this:
#include <iostream>
#include <string>
#include <algorithm>
int main()
{
srand(time(0));
int matrix[5][20];
int *pmatrix = &matrix[0][0];
int i = 0;
for (i = 0; i < 100; i++)
{
pmatrix[i] = i+1;
}
std::random_shuffle(pmatrix, pmatrix+100);
for (i = 0; i < 100; i++)
{
std::cout<<pmatrix[i]<<",";
}
}
cpp.sh/5bnyt
Update fixed memory out of bounds problem.