I am using VS 2017. I am attempting to open a text file that the user inputs and read the integers from that text file and then output the largest and smallest numbers from that text file.
Issues:
I cannot seem to figure out how to open a user generated text file.
it skips the loop entirely and does not read any numbers from the text file.
Any help would be greatly appreciated.
Right now my output is Max: 0 Min: 0
This is my source code:
#include <iostream>
#include <fstream>
#include <string>
using namespace std;
int main()
{
ifstream fin;
double min = 0;
double max = 0;
int next;
double sum = 0;
string fileName;
cout << "Enter the name of the file you would like to use: " << endl;
cin >> fileName;
fin.open(fileName.c_str());
if (fin.fail())
{
cout << "Input file opening failed." << endl;
exit(1);
}
while (fin >> next)
{
if (next > max)
{
max = next;
}
if (next < min)
{
min = next;
}
}
cout << "Min: " << min << " Max: " << max;
return 0;
}
Related
I am trying to solve a question called 'smurf' on codebreaker.xyz, but my code is too slow. The task is to take in a series of numbers, one at a time, and reverse the array each time.
So for this input:
6
0 1 2 1 2 0
it should give the output 0 1 1 0 2 2.
The logic is correct and the code works, but how can I make it execute under 1 second for s <= 200,000...
This is the code in C++17:
#include <algorithm>
#include <bits/stdc++.h>
using namespace std;
#define int unsigned int
vector<int> S;
int s, t;
int32_t main(){
ios_base :: sync_with_stdio(false); cin.tie(0); cout.tie(0);
cin >> s;
for(int i = 0; i < s; i++){
cin >> t;
S.push_back(t);
reverse(S.begin(), S.end());
}
for(int j = 0; j < s; j++){
cout << S[j] << " ";
}
}
As I understand your question, you need to reverse your container every time you add a new element. We can omit that by just adding the new number to the back or the front of the container, depending on if the container should be "reversed" or not at the moment. Since adding elements to the front of a vector is quite costly I would suggest using a list instead. An example would look like this
#include <iostream>
#include <list>
#include <ranges> //c++20
int main() {
std::list<int> numbers{};
bool reversed = false;
int N;
std::cin >> N;
while (N>0) {
int inputNumber;
std::cin >> inputNumber;
if(reversed){
numbers.push_front(inputNumber);
}
else{
numbers.push_back(inputNumber);
}
reversed = not reversed;
--N;
}
if(reversed){
for(const int i : numbers | std::views::reverse){
std::cout << i << ' ';
}
}
else{
for(const int i : numbers){
std::cout << i << ' ';
}
}
}
I am beginner in UI design using Qt. My project now is doing comparison. For example: if I have 2 text file.
How can I compare the number line by line? Because I have so many text file like this, and I need compare them on by one.What I can do now is only read the text file by line order. Thank you so much!
The procedure is simple
Read both files (always make sure they are opened successfully)
Read files line by line and convert strings to numbers for comparison.
Quit if there is no data left.
Moreover, you need to make sure that the format of files is consistent otherwise, you need to make sure what you manipulate is a real number. I assume numbers are integers but of course you can change it. Extra precautions are required in this kind of project. I will leave it to you. The simplified code for the above procedure is
#include <QString>
#include <QFile>
#include <QDebug>
#include <QTextStream>
int main()
{
QFile data1("text1.txt");
if (!data1.open(QIODevice::ReadOnly | QIODevice::Text)){
qDebug() << "text1.txt file can't be opened...";
return -1;
}
QFile data2("text2.txt");
if (!data2.open(QIODevice::ReadOnly | QIODevice::Text)){
qDebug() << "text2.txt file can't be opened...";
return -1;
}
QTextStream in1(&data1), in2(&data2);
while ( !in1.atEnd() && !in2.atEnd() ) {
QString num1 = in1.readLine();
QString num2 = in2.readLine();
if ( num1.toInt() > num2.toInt() )
qDebug() << num1.toInt() << ">" << num2.toInt();
// do the rest of comparison
}
return 0;
}
Now in my case, the txt files are
text1.txt
1
2
3
4
text2.txt
3
5
1
6
The output is
3 > 1
Edit: the OP is looking for the difference and its sum.
int sum(0);
while ( !in1.atEnd() && !in2.atEnd() ) {
QString num1 = in1.readLine();
QString num2 = in2.readLine();
int result = num1.toInt() - num2.toInt();
qDebug() << num1.toInt() << "-" << num2.toInt() << " = " << result;
sum += result;
}
qDebug() << "sum = " << sum;
Basic approach would be something like this:
QString filename1("C:/Users/UserName/Downloads/t1.txt");
QString filename2("C:/Users/UserName/Downloads/t2.txt");
QFile file(filename1);
file.open(QIODevice::ReadOnly);
QTextStream in(&file);
QStringList textOfFile1;
while (!in.atEnd()) {
QString line = in.readLine();
textOfFile1.append(line);
}
QFile file2(filename2);
file2.open(QIODevice::ReadOnly);
QTextStream in2(&file2);
QStringList textOfFile2;
while (!in.atEnd()) {
QString line = in.readLine();
textOfFile2.append(line);
}
if(textOfFile1.size() != textOfFile2) return false;
for(int i = 0; i < textOfFile1.size(); i++)
{
if(textOfFile1[i] != textOfFile2[i]) return false;
}
return true;
i.e. You read the files into a QStringList and you compare the lists line by line. This way you can also catch the firs # of line where there was a mismatch. Note that such comparison also considers white spaces such as \n \t etc.
PS: wrap the readers into functions, to avoid duplication like me. :)
Hope this helps ;)
In SQLite if I prepare a SELECT statement and begin stepping through it, then before the last row of the results is reached I execute another statement that has an effect on the SELECT statement that I am stepping through, what is the expected result?
I can't find anything in the SQLite documentation about what is supposed to happen but it seems like an extremely common case when programming in a multi-threaded environment.
Below is a c++ file that can be compiled and run on Windows to demonstrate the situation.
#include "stdafx.h"
#include "sqlite3.h"
#include <Windows.h>
#include <iostream>
#include <Knownfolders.h>
#include <Shlobj.h>
#include <wchar.h>
#include <comdef.h>
using namespace std;
int exec_sql(sqlite3 *db, const char* sql)
{
char *errmsg;
int result = sqlite3_exec(db, sql, NULL, NULL, &errmsg);
if (result != SQLITE_OK) {
cout << errmsg << endl;
return -1;
}
return 0;
}
int _tmain(int argc, _TCHAR* argv[])
{
cout << "Running jsqltst with SQLite version: ";
cout << sqlite3_libversion();
cout << endl;
PWSTR userhome;
if (!SUCCEEDED(SHGetKnownFolderPath(FOLDERID_Profile, NULL, NULL, &userhome))) {
cout << "Failed getting user home dir\n";
return -1;
}
wcout << "User home: " << userhome << endl;
wchar_t *ws1 = userhome, *ws2 = L"\\test.sqlite";
wstring dbpath_str(ws1);
dbpath_str += wstring(ws2);
_bstr_t dbpath(dbpath_str.c_str());
cout << "DB path: " << dbpath << endl;
sqlite3 *db;
int result = sqlite3_open_v2(dbpath, &db, SQLITE_OPEN_READWRITE|SQLITE_OPEN_CREATE, NULL);
if (result != SQLITE_OK) {
cout << sqlite3_errmsg(db) << endl;
return -1;
}
const char * create_stmt = "CREATE TABLE IF NOT EXISTS atable (id INTEGER PRIMARY KEY, name TEXT, number INTEGER);";
if (exec_sql(db, create_stmt) != 0) {
return -1;
}
const char * delete_stmt = "DELETE FROM atable;";
if (exec_sql(db, delete_stmt) != 0) {
return -1;
}
const char * insert_stmt = "INSERT INTO atable (name,number) VALUES ('Beta',77),('Alpha',99);";
if (exec_sql(db, insert_stmt) != 0) {
return -1;
}
sqlite3_stmt* select_ss;
const char * select_stmt = "SELECT * FROM atable;";
result = sqlite3_prepare_v2(db, select_stmt, -1, &select_ss, NULL);
if (result != SQLITE_OK) {
cout << sqlite3_errmsg(db) << endl;
return -1;
}
int i = 0;
boolean gotrow;
do {
result = sqlite3_step(select_ss);
gotrow = result == SQLITE_ROW;
if (gotrow) {
i++;
cout << "I got a row!" << endl;
if (i == 1) {
if (exec_sql(db, insert_stmt) != 0) {
return -1;
}
}
}
} while (gotrow);
cout << "Last result: " << result << ", errstr: " << sqlite3_errstr(result) << endl;
result = sqlite3_finalize(select_ss);
if (result != SQLITE_OK) {
cout << sqlite3_errmsg(db) << endl;
return -1;
}
return 0;
}
SQLite's behaviour for concurrent statements in the same transaction is neither documented nor defined.
As you have seen, newly inserted records might be seen when a SELECT's cursor has not yet reached that part of the table.
However, if SQLite needed to create a temporary result table for sorting or grouping, later changes in the table will not appear in that result.
Whether you have a temporary table or not might depend on decisions made by the query optimizer, so this is often not predictable.
If multiple threads access the same connection, SQLite will lock the DB around each sqlite3_step call.
This prevent data corruption, but you will still have the problem that automatic transaction end when their last active statement ends, and that explicit transaction will fail the COMMIT if there is some other active statement.
Multi-threaded programs are better off using (at least) one connection per thread.
//#include <QtCore/QCoreApplication>
#include <stdio.h>
#include <stdlib.h>
#include <iostream>
#include <string>
#include "shift.h"
using namespace::std;
int main(int argc, char *argv[])
{
unsigned char tmpBuf;
FILE* fp;
FILE* fp2;
char fname[50];
static unsigned int lSize, count, num;
cout << "Input the filename:" << endl;
cin >> fname;
fp = fopen(fname,"r");
if(fp == NULL) {
cout << "The file does not exist!" << endl;
exit(1);
}
// obtain file size:
fseek(fp , 0 , SEEK_END);
lSize = ftell(fp);
rewind(fp);
cout << "The intput file's size is: " << lSize << endl;
fp2 = fopen("myfile", "w");
while(1){
num = fread(&tmpBuf, 1, 1, fp);
count += num;
// putchar(tmpBuf);
// tmpBuf = cror(tmpBuf, 4);
// tmpBuf = crol(tmpBuf, 4);
fwrite(&tmpBuf, 1, num, fp2);
cout << tmpBuf << " " << num << " " << count << endl;
if (count == lSize){
printf("over\n");
break;
}
}
fclose(fp);
fclose(fp2);
while(1){}
return 0;
//return a.exec();
}
I made a Qt console program and disable QtCore, like above code. When read some file, e.g. 1.txt (which contains only 1234567890) it succeeds. But when reading some other file, e.g. 1.rar, it failed like below: Why?
Check the value of num coming back from
num = fread(&tmpBuf, 1, 1, fp);
If it comes back as 0, that would explain why
if (count == lSize){
never comes back as true to break you out of the loop.
As to why that could happen, you're opening fname in "r" mode but a rar file would be binary. For that, I'd suggest opening in "rb" mode. If fread expects txt format but hits the EOF indicator, it'll stop advancing so num = 0 and count won't increase.
I don't have windows available to test this, but other questions have come up on stackoverflow for this reason:
fread/ftell apparently broken under Windows, works fine under Linux
I am a novice C++ coder and obviously not very good at it. I am having an immense amount of trouble with this program.
I am getting syntax errors on my opening and closing parenthesis on my functions, syntax errors on my "<" in my header cpp file, and errors that I'm missing parenthesis.
My first stack is not recognized (main driver file) and in my StackType.cpp file - original is an "undeclared identifier".
Lastly, the left of Push must have class/struct/union - in my for loop when filling the first stack with the rings.
I apologize for all of these issues in advance. Any help you could give me would be greatly appreciated!
Thank you.
======================Stack Header================================
// File: StackType.h
// Stack template class definition.
// Dynamic array implementation
#ifndef StackType
#define StackType
template <class ItemType>
class StackType
{
private:
int ItemType;
ItemType *myStack; // pointer to dynamic array
int _top, _maxSize; // using underscores to remind that it's private
public:
StackType(int numRings = 50); // Constructor
StackType (const StackType<ItemType>&); // Copy Constructor
// Member Functions
void Push(ItemType); // Push
void Pop(ItemType &); // Pop
void stackTop(ItemType &) const; // retrieve top
bool stackIsEmpty() const; // Test for Empty stack
bool stackIsFull() const; // Test for Full stack
~StackType(); // Destructor
};
#endif
=====================Stack cpp file==================================
#include "StackType.h"
#include "stdafx.h"
#include <iostream>
#include <stdio.h>
// Constructor with argument, size is numRings, limit is 50 (set in .h header)
template <class ItemType>
StackType<ItemType>::StackType()
{
_maxSize = numRings;
_top = -1;
}
// Copy Constructor
template <class ItemType>
StackType<ItemType>::StackType(const StackType<ItemType>& original :
_maxSize(original._maxSize), top(original._top)
{
myStack = new ItemType[_maxSize];
for (int i = 0; i <= top; i++) myStack[i] = original.myStack[i];
}
// Destructor
template <class ItemType>
StackType<ItemType>::~StackType()
{
delete [] myStack;
}
// Push
template <class ItemType>
void StackType<ItemType>::Push(StackType<ItemType> ringVal)
{
if(stackIsFull()) cout << "\t There is not enough available memory = the stack is
full!" << endl;
else myStack[++_top] = ringVal;
}
// Pop
template <class ItemType>
void StackType<ItemType>::Pop(StackType<ItemType> &ringVal)
{
if(stackIsEmpty()) cout << "\t The stack is empty!" << endl;
else ringVal = myStack[_top--];
}
// Retrieve stack top without removing it
template <class ItemType>
void StackType<ItemType>::stackTop(StackType<ItemType> &ringVal) const
{
if(stackIsEmpty()) cout << "The stack is empty!";
else ringVal = myStack[_top];
}
// Test for Empty stack
template <class ItemType>
bool StackType<ItemType>::stackIsEmpty() const
{
return (_top < 0);
}
// Test for Full stack
template <class ItemType>
bool StackType<class ItemType>::stackIsFull() const
{
return (_top >= (_maxSize - 1));
}
// end StackType.cpp
=========================Main Driver file=======================================
#include "StackType.h"
#ifdef _DEBUG
#include "StackType.cpp"
#endif // _DEBUG
#include <stack>
#include "StdAfx.h"
#include <iostream>
using namespace std;
// Global Variable - Counter to display the number of moves.
int count = 0;
class StackType;
// Functions Prototypes
void MoveRings(StackType<ItemType>&, StackType<ItemType>&);
// Function to move the rings
void Pegs(int D,StackType<ItemType>& b,StackType<ItemType>& e, StackType<ItemType>& h);
// This is a recursive function.
void Display (int, StackType <ItemType>& , StackType<ItemType>&, StackType<ItemType>&);
// Function to display the pegs
// Main - Driver File
int main()
{
// create 3 empty stacks
StackType<ItemType> FirstPeg; // Receiving an error that this is not identified
StackType<ItemType> EndPeg;
StackType<ItemType> HelperPeg;
// Number of rings.
int numRings;
cout << "\n\t *********** Rings to Pegs (Towers of Hanoi) ***********\n" << endl;
cout << "\t Please Enter the number of rings you want to play with: ";
// Input number of rings
cin >> numRings;
cout << endl;
while(numRings < 0 || isalpha(numRings)) // To make sure that the user did not
// enter an invalid number
{
cout << " Your entry is invalid. Please use only integers. Please re-
enter: ";
cin >> numRings;
cout << endl;
}
for(int i = 1; i <= numRings; i++)
// Fill the first peg with the number of rings.
{
FirstPeg.Push(i);
}
Pegs(int, StackType<ItemType>&, StackType<ItemType>&, StackType<ItemType>&);
// To call the recursive function that will move the rings
Display (int, StackType<ItemType>&, StackType<ItemType>&, StackType<ItemType>&);
// To call the display function
cin.clear();
cin.ignore('\n');
cin.get();
return 0;
}
// This function will move an ring from first peg to the second peg
void MoveRings(StackType<ItemType>& beg, StackType<ItemType>& theEnd) //End
{
int r; // disk will be removed from one stack and added to the other
beg.Pop(r);//pop from source
theEnd.Push(r);//and move to target
}
// This function displays the moves
void Display(int R, StackType<ItemType>& toBegin , StackType<ItemType>& toEnd,
StackType<ItemType>& toHelp)
{
StackType<int> B;// create temporarily first stack
StackType<int> E;// create temporarily End(End) stack
StackType<int> H;// create temporarily helper stack
for(int i = 1; i <= R; i++)
{
toBegin.Pop(i);//moves the ring from source
B.Push(i);//to the temporarily stack to display it
cout << "Beginning Peg:" << &B << endl;
toEnd.Pop(i);//moves the ring from source
E.Push(i);//to the temporarily stack to display it
cout << " End(Final) Peg: " << &E << endl;
toHelp.Pop(i);//moves the ring from source
H.Push(i);//to the temporarily stack to display it
cout << " Helper Peg:" << &H << endl;
}
}
//-------------------------------------------------------------------
void Pegs(int D,StackType<ItemType>& b,StackType<ItemType>& e,StackType<ItemType>& h)
// This is a recursive function.
{
if (D == 0) // The base
{
return 1;
}
else if(D == 1) // If there is only one ring, move this ring from the
// first peg to the end(final) peg
{
MoveRings(b, e); // moves the ring from the first to the end(final) peg
cout<<" Really? You have entered one ring..." << endl;
cout<<" It moves directly from the first peg to the End peg." << endl;
count++; // increment the number of moves
cout << "There has been " << count << " move. "<< endl;// display the
// number of moves
Display (D, b, e, h);
}
else if (D > 1) // a recursive function in order to move the rings
{
Pegs(D - 1, b, e, h); // to move N-1 rings from the first peg to the
// end(final) peg by using the helper peg
MoveRings(b, e);// to move the last ring to the end(final) peg
count++; // increment the number of steps before displaying
cout << "There has been " << count << " moves. "<< endl;
Pegs(D - 1, b, e, h);
// to move N-1 rings from the helper peg to the end(final) peg with the help of
// first peg
//Display ( D(rings), First Peg, End(Final) Peg, Helper Peg );
}
}
One problem that I can see immediately is that your header file defines StackType to prevent double inclusion, which is also used as a class name. After #define StackType, it ends up being a macro that expands to nothing, so your code looks like class { ... }.
You should use a symbol to prevent double inclusion that isn't used for anything else. The typical thing to use is STACKTYPE_H for a file called StackType.h.
Once you've fixed this, some other problems you're experiencing might go away. Please come back with an update if you're having more problems, and post the exact compiler errors if you do.