I have an assignment with several ways to manipulate an array, but I'm having trouble with one of the parts.
I am reading about 50 numbers into the array from a .txt file
And for every odd location in the array (1,3,5,…), I have to subtract it from the previous even location (0,2,4,…) and store results in the odd location. Then I print out all values in the array.
Here is what I have so far:
void oddMinusEven(int ary[],int num)
{
for(int idx = ary[0]; idx<num; ary[idx+2])
{
ary[idx] = ary[idx+2]-ary[idx];
cout<<ary[idx]<<endl;
}
}
How do I do this? If you could provide some examples, that would be great.
This should do:
void oddMinusEven(int ary[], int num) {
for(int i = 1; i < num; i += 2) {
ary[i] = ary[i-1] - ary[i];
std::cout << "a[" << i << "] = " << ary[i] << std::endl;
}
}
Related
Here I am using Data Structure Queues to change cards places using strings. User picks the top card than put it at last of the deck. The problem is that I need to return updated string to main. What it is returning is junk Values. I also tried to copy the string array and than returning that arraybut didn't work. Can anyone help?
#include<iostream>
#include<string>
using namespace std;
string CommunityChest(string Cards[]){
struct Que{
string cards[6];
int front =0;
int back=-1;
}ComQ;
string temp;
for(int i=0; i<5;i++)
{//Enqueue(Cards)
ComQ.back++;
if(ComQ.back<=5)
{
ComQ.cards[ComQ.back]=Cards[i];
}
else{
cout<<"Overflow";
}
}
//Display
for(int i=ComQ.front; i<=ComQ.back; i++)
{
cout<<ComQ.cards[i]<<endl;
}
//Del()
if(ComQ.front>=0)
{
temp=ComQ.cards[ComQ.front];
ComQ.front++;
}
cout<<endl<<"Pick the top Card"<<endl;
cout<<temp<<endl;
//EnQ the picked card
ComQ.back++;
if(ComQ.back<=5)
{
ComQ.cards[ComQ.back]=temp;
}
else{
cout<<"Overflow";
}
cout<<endl<<"After Inserting top card:"<<endl;
//Display
string newQ1[5];
for (int i=ComQ.front; i<=ComQ.back; i++) //Making an alternate array to copy Comq.cards array data
{
newQ1[i]=ComQ.cards[i];
}
for(int i=0; i<5; i++)
{
return newQ1[i]; //trying to return string array
//cout<< newQ1<<endl;
}
}
int main(){
string cards[5]{ "1 Advance ........",
"2. It is your ...........",
"3. You have won .............",//Cards as strings
"4. From sale of..............",
"5. Pay Hospital............"};
string newQ1=CommunityChest(cards);
for(int i=0; i<5; i++)
cout << newQ1[i] << endl;
return 0;
}
There are some issues with this code as mentioned in the comments, you are trying to do a return in a loop, this may look okay but it's wrong since a return can get you out of the function. But it seems like you want to return an array of strings.
A fix for this function would be like this:
#include <iostream>
std::string* CommunityChest(std::string Cards[]) {
struct Que {
std::string cards[6];
int front = 0;
int back = -1;
} ComQ;
std::string temp;
for (int i = 0; i < 5; i++) { // Enqueue(Cards)
ComQ.back++;
if (ComQ.back <= 5) {
ComQ.cards[ComQ.back] = Cards[i];
}
else {
std::cout << "Overflow";
}
}
// Display
for (int i = ComQ.front; i <= ComQ.back; i++) {
std::cout << ComQ.cards[i] << std::endl;
}
// Del()
if (ComQ.front >= 0) {
temp = ComQ.cards[ComQ.front];
ComQ.front++;
}
std::cout << std::endl
<< "Pick the top Card" << std::endl;
std::cout << temp << std::endl;
// EnQ the picked card
ComQ.back++;
if (ComQ.back <= 5) {
ComQ.cards[ComQ.back] = temp;
}
else {
std::cout << "Overflow";
}
std::cout << std::endl
<< "After Inserting top card:" << std::endl;
// Display
// Creating a dynamic array to store the values
std::string* newQ1 = new std::string[5];
for (int i = ComQ.front, j = 0; i <= ComQ.back && j < 5; i++, j++) {// Making an alternate array to copy Comq.cards array data
newQ1[j] = ComQ.cards[i];
}
return newQ1; // Returning the dynamic array
}
int main()
{
std::string cards[5]{
"1 Advance ........",
"2. It is your ...........",
"3. You have won .............", // Cards as strings
"4. From sale of..............",
"5. Pay Hospital............"
};
std::string* newQ1 = CommunityChest(cards);
for(int i = 0; i < 5; i++) {
std::cout << newQ1[i] << std::endl;
}
delete[] newQ1; // Deleting the array
return 0;
}
The output will be:
1 Advance ........
2. It is your ...........
3. You have won .............
4. From sale of..............
5. Pay Hospital............
Pick the top Card
1 Advance ........
After Inserting top card:
2. It is your ...........
3. You have won .............
4. From sale of..............
5. Pay Hospital............
1 Advance ........
In this fix, I'm returning a dynamically allocated array of strings because a static array will be destroyed once the scope ends, it would be better sometimes to use other ways to allocate memory such as std::unique_ptr<> or std::shared_ptr<>, but I'd suggest you learn how to do it yourself first then use those when needed.
EDIT:
You can also return an std::array<>, I suggest you to read about it as C-Style arrays cannot be returned in you way that you tried and can't be returned without using dynamic allocation, so an std::array<> can be a good replacement over std::string* in this case
there is code.
#include "pch.h"
#include <algorithm>
#include <iostream>
#include <vector>
#include <stdlib.h>
using namespace std;
vector<int> SearchInt(vector<int> vec, int num) {
vector<int> temp(2);
sort(begin(vec), end(vec));
int j = 0;
for (int i : vec) {
if (i > num) {
temp[0] = i;
temp[1] = j;
return { temp };
}
//cout << i << " !>= " << num << endl ;
j++;
}
cout << "NO";
exit(0);
}
int main()
{
int n;
cin >> n;
vector<int> nums(n, 0);
vector<int> NewNums(n, 0);
for (int i = 0; i < n; i++) {
cin >> nums[i];
}
if (n != nums.size()) {
cout << "://";
return 0;
}
sort(begin(nums), end(nums));
NewNums[1] = nums[nums.size() - 1];
nums.erase(nums.begin() + nums.size() - 1);
NewNums[0] = nums[nums.size() - 1];
nums.erase(nums.begin() + nums.size() - 1);
for (int j = 2; j <= NewNums.size() - 1; j++) {
NewNums[j] = SearchInt(nums, NewNums[j-1]- NewNums[j-2])[0];
nums.erase(nums.begin() + SearchInt(nums, NewNums[j] - NewNums[j - 1])[1]);
}
if (NewNums[NewNums.size()-1] < NewNums[NewNums.size() - 2] + NewNums[0]) {
cout << "YES" << endl;
for (int i : NewNums) {
cout << i << " ";
}
return 0;
}
else {
cout << "NO";
return 0;
}
}
His task is to check whether it is possible from the given Each number is less than the sum of the two adjacent ones.
(each number is less than both of two adjacent ones)
But there is a problem - with a large number of numbers, the code takes too long. Please help me to optimize it, or just give some advice.
numbers cаn not be null.
time limit: 3.0 s
n <= 500000
You are given n numbers a1, a2,…, an. Is it possible to arrange them in a circle so that each number is strictly less than the sum of its neighbors?
For example, for the array [1,4,5,6,7,8], the left array satisfies the condition, while the right array does not, since 5≥4 + 1 and 8> 1 + 6.
Input data
The first line contains one integer n (3≤n≤105) - the number of numbers.
The second line contains n integers a1, a2,…, an (1≤ai≤109) - the numbers themselves. The given numbers are not necessarily different.
Output
If there is no solution, print "NO" on the first line.
If it exists, print "YES" on the first line. After that, on the second line print n numbers - the elements of the array in the order in which they will stand on the circle. The first and last elements you print are considered neighbors on the circle. If there are multiple solutions, output any of them. You can print a circle starting with any of the numbers.
First I'll only briefly analyze technical shortcomings of your code - without analyzing its meaning. After that I'll write my solution of the problem you defined.
Performance problems of your code are due to some strange decisions:
(1) passing std::vector<int> by value and not by reference to SearchInt function - this implies allocating and copying of the whole array on each function invocation,
(2) call SearchInt two times per loop iteration in function main instead of only one,
(3) sort array within each invocation of SearchInt - it is already sorted before the loop.
To be honest your code feels ridiculously time-consuming. I'm only wondering if that was your intention to make it as slow as you possibly can...
I will not analyze correctness of your code according to problem description. To be honest even after fixing technical shortcomings your code seems to me utterly sub-optimal and quite incomprehensible - so it is just easier to solve the problem from scratch to me.
The answer to the problem as defined is YES if the biggest number is smaller than the sum of the second big and the third big and NO otherwise - this follows from the fact that all numbers are positive (in range 1 - 109 according to newly found problem description). If the answer is YES then to make a circle that satisfies the problem description you just need in a sorted sequence of input numbers switch places of the biggest number and the next big one - that's all.
Here is my code for that (for slightly relaxed input format - I'm not checking if number of items is on a separate line and that all items are on the same line - but all correct inputs will be parsed just fine):
#include <set>
#include <iostream>
int main()
{
std::multiset<unsigned> input_set;
unsigned n;
if( !( std::cin >> n ) )
{
std::cerr << "Input error - failed to read number of items." << std::endl;
return 2;
}
if( n - 3U > 105U - 3U )
{
std::cerr << "Wrong number of items value - " << n << " (must be 3 to 105)" << std::endl;
return 2;
}
for( unsigned j = 0; j < n; ++j )
{
unsigned x;
if( !( std::cin >> x ) )
{
std::cerr << "Input error - failed to read item #" << j << std::endl;
return 2;
}
if( x - 1U > 109U - 1U )
{
std::cerr << "Wrong item #" << j << " value - " << x << " (must be 1 to 109)" << std::endl;
return 2;
}
input_set.insert(x);
}
std::multiset<unsigned>::const_reverse_iterator it = input_set.rbegin();
std::multiset<unsigned>::const_reverse_iterator it0 = it;
std::multiset<unsigned>::const_reverse_iterator it1 = ++it;
if( *it0 >= *it1 + *++it )
{
std::cout << "NO (the biggest number is bigger than the sum of the second big and the third big numbers)" << std::endl;
return 1;
}
std::cout << "YES" << std::endl;
std::cout << "Circle: " << *it1 << ' ' << *it0;
do
{
std::cout << ' ' << *it;
}
while( ++it != input_set.rend() );
std::cout << std::endl;
return 0;
}
The basic problem is that we (in pairs) have been tasked with creating a program to - amongst other things - read in a txt file and display it as a sudoku board as part of our introduction to coding at Uni.
We have completed most of the code and have got it working sufficiently well. However, we are struggling with what I would consider to be a basic aspect of this. The code reads in the file and saves it to the classes private char 9*9 matrix. We have run a debugging print-out to check that the values are being saved to the matrix and this is indeed the case. The issue is with the getMatrixVal(int x, int y) function which we think is returning a pointer rather than the character. We have tried returning a pointer from the function and have tried saving to a pointer and then to a char variable. Unfortunately, we am not excellent on pointer's.
With the recent suspensions to University timetables, we are temporarily unable to get the advice and support we require and, hence, we are applying here for advice.
Also, we are using the qt programming software on a raspberry pi - could this have anything to do with our problems?
#include "grid.h"
#include <QDebug>
#include <QChar>
#include <QFile>
grid::grid(char matrix_value, const int x, const int y) {
matrix[x][y] = matrix_value;
//char c = matrix[x][y];
//qDebug() << QChar(c);
}
void grid::load_file() {
QFile file("/home/pi/Documents/ELEC1204/P6/SUDOKU.txt");
char character, c;
int i, j;
if(!file.open(QFile::ReadOnly)) {
qDebug() << "Error in opening file";
return;
} //Print error if message if unable to open file
for(i = 0; i < 9; i++) {
for(j = 0; j < 9; j++) {
SKIP: //Related to 'goto'
file.read(&character, sizeof(char)); //Read ini individual characters
if(character == '\xd' || character == '\xa')
goto SKIP;
//Skip character related to new lines
//Goes to 'SKIP' point in program
else if(character == 'X')
grid('_', i, j);
//Save 'X's as '_'
else
grid(character, i, j);
//Save numbers as they are
c = getMatrixVal(i, j);
qDebug() << "i = " << i << "| j = " << j << "| Character is: " << QChar(character) << "| Matrix character is: " << QChar(c);
//Print-out for debugging
}
}
file.close();
//Close file
}
// Possibly useful source:
// https://doc.qt.io/qt-5/qfile.html
// https://forum.qt.io/topic/60240/reading-file-byte-by-byte/5
char grid::getMatrixVal(const int x, const int y) {
char c = matrix[x][y];
//qDebug() << "Matrix[" << x << "][" << y << "] is: " << QChar(c);
return c;
}
void grid::printMatrix() {
for(int i = 0; i < 9; i++) {
for(int j = 0; j < 9; j++) {
qDebug() << matrix[i][j];
}
}
}
//Prints out matrix
//Debugging function
There is nothing wrong with getMatrixVal: it returns a character from the right place in matrix.
Your call grid(character, i, j) constructs a new grid instance that is unrelated to the current one.
Instead, just assign directly to matrix: (or use a setter function)
matrix[i][j] = character;
I'm having an interesting problem when I'm accessing a double vector. The idea is that I have deleted all information prior to accessing the vector. A for loop tries to access the vector and successful says that the vector is empty, but when I access the vector point directly it shows that there are variables still in the vector.
Also, the vector was set up like so:
vector<vector<string>> proTable;
Here is the loop attempting to access the vector.
for(int a = 0; a < proTable.size(); a++)
{
for(int b = 0; b < proTable[a].size(); b++)
{
cout << proTable[a][b] << "\t";
}
}
But if I edit the for loop this way it returns the variable inside.
for(int a = 0; a < proTable.size(); a++)
{
for(int b = 0; b < proTable[a].size(); b++)
{
cout << proTable[a][b] << "\t";
}
cout << proTable[0][0];
}
The first prints nothing out. The second prints X which was in the vector before. Also, the vector does not show that it is empty.
This is how I was deleting it if it matters.
void MRelation::RemoveColumn(vector<int> rem)
{
while(!rem.empty())
{
int z = rem[rem.size() - 1];
for(int a = 0; a < proTable.size(); a++)
{
for(int b = z; b < proTable[a].size() - 1; b++)
{
proTable[a][b] = proTable[a][b+1];
}
proTable[a].pop_back();
}
rem.pop_back();
}
}
The vector rem holds the columns that need to be deleted from the table.
I have deleted all information prior to accessing the vector.
Accessing an vector out of bounds has undefined behaviour. Since your vector is empty, proTable[0] is out of bounds. In the line cout << proTable[0][0];, you access proTable[0]. Therefore the behaviour of your program is undefined.
it shows that there are variables still in the vector.
You cannot jump to such conclusion from observing undefined behaviour.
"There are variables still in the vector" was not necessarily the reason why you saw output. You saw output because the behaviour was undefined.
I found out what it was. I you delete the contents of the inner vector but don't delete the vectors themselves then the vector will think that it contains something still and will pull out information that doesn't exist anymore. here is the code I was have problems with. It has been edited with an if statement to correct it.
void MRelation::FinalPrint()
{
if(curTable.size() < 2)
{
ss << "? No\n";
}
else
{
ss << "? Yes(" << curTable.size() - 1 << ")\n";
}
if(!proTable[0].empty()) //This was added in after to correct the problem
{
for(int c = 1; c < proTable.size(); c++)
{
ss << " " << proTable[0][0] << "=" << proTable[c][0];
for(int d = 1; d < proTable[0].size(); d++)
{
ss << ", ";
ss << proTable[0][d] << "=" << proTable[c][d];
}
ss << "\n";
}
}
}
Sorry about not putting everything in context before. I was trying to put in as much relavant information without putting in 300 lines of code.
I basically want to pass this array of data I'm reading to diffent functions and eventually plot it.
The array contains a 32 bit word of '1's and '0's, I then want to add these individual bits together to see where my data spikes. So in other words if I add "0100" to "0110" I get "0210" - which is probably easier done with separate bins and plotting.
At the moment I'm just getting garbage out.
void binary(int convert, int* dat) {
bitset<32> bits(convert);
//cout << bits.to_string() << endl;
char data[32];
for(unsigned i = 0; i < 32; ++i) {
data[i] = bits[i];
}
for(unsigned i = 32; i; --i) {
dat[i] = (int(data[i-1]))+dat[i];
}
}
void SerDi() {
int dat[32];
cout << " Reading data from memory..." << endl;
ValVector< uint32_t> data=hw.getNode("SerDi.RAM").readBlock(8);
hw.dispatch();
cout << data[0]<<endl;
cout << data[1]<<endl;
for (unsigned i = 2; i < 7; i++) {
binary(data[i], dat);
}
cout << dat[7] << endl;
graph(dat); //passes the array to a place where I can plot the graph
}
You have
int dat[32];
But in convert you have i = 32 and dat[i] That will access something outside of the array and bad things will happen.
Also that is not initialized. Add a memset/loop somewhere to make dat initially 0.