I have a 2d vector where the rows are unequal. I have been trying to delete the first column but have no luck look at previous stackoverflow posts.
example data:
1 2 4 5 6 6
1 2 3 4 6 6 8
Code to read in data:
myfile.open("test.txt");
if(myfile.is_open())
{
while(getline(myfile, line)){
//cout << "This line: ";
if(line != "")
{
istringstream is(line);
sortVec.push_back(std::vector<int>( std::istream_iterator<int>(is),
std::istream_iterator<int>() ) );
}
}
}
else
{
cout << "Myfile is not open" << endl;
}
myfile.close();
When I try to erase the first column using std:vector:
int columnIndex = 0;
for(auto& row:sortVec){
row.erase(next(row.begin(), columnIndex));
}
I get a segmentation fault.
I have tried the following stackoverflow posts as well.
How to delete column in 2d vector, c++
Additionally when I create a vector manually everything works perfect so I am lost at the moment.
Desired output:
2 4 5 6 6
2 3 4 6 6 8
The answer was that don't forget to check empty lines when using getline. The last line of my file was empty.
Related
I'm trying to read in this text file:
8 4 4 6 1
8 4 4 6 2
8 4 4 6 3
8 4 4 6 4
8 4 4 6 5
8 4 4 6 6
8 4 4 6 7
8 4 4 6 8
11 4 4 6 3
15 11 13
7 2 1 4 4
9 4 3 9 9
8 2 1 5 4
10 1 2 3 4 6 1
6 1 1 2 5 3 2
13 1 1 2 10 3 8
11 2 11 10 7
And printing it exactly as shown to the console (to make sure I got every input).
However, for some reason my code crashes after reading in the first line. I can't even terminate the debugger.
Here's my code:
while(getline(inFile, buffer)){
buffer2 = strdup(buffer.c_str());
line = strtok(buffer2, " ");
size = atoi(line);
cout << size << " ";
while(line!=NULL){
line = strtok(NULL, " ");
cout << line << " ";
}
cout << "~~~~~~~~~" << endl;
}
If you are going to use C++ you should take advantage of that, use string streams:
#include <fstream>
#include <sstream>
#include <iostream>
using namespace std; //for sample purposes, should not be used
int main() {
int temp, count = 0, sum = 0, total = 0;
string buffer;
ifstream myFile("in.txt");
if (!myFile.is_open())
cout << "No file" << endl;
else{
while(getline(myFile, buffer)){
sum = 0;
stringstream ss(buffer);
while(ss >> temp){
count++; //number count
sum += temp; //line sum
cout << temp << " ";
}
total += sum; //total sum
cout << endl << "count: " << count << endl
<< "sum: " << sum << endl << "total: " << total << endl << endl;
}
myFile.close();
}
cout << "~~~~~~~~~" << endl;
}
You are leaking the memory allocated by strdup(). You need to call free() when you are done using buffer2.
But more importantly, strtok() returns NULL when there are no more tokens to return. But it is undefined behavior to pass a NULL char* pointer to operator<<. Your while loop is doing exactly that when it reaches the end of each line, so anything could happen, including crashing.
Try this instead:
while (getline(inFile, buffer)) {
buffer2 = strdup(buffer.c_str());
if (buffer2 != NULL) {
line = strtok(buffer2, " ");
while (line != NULL) {
size = atoi(line);
cout << size << " ";
line = strtok(NULL, " ");
}
free(buffer2);
}
cout << "~~~~~~~~~" << endl;
}
That being said, why are you using strdup(), strtok(), and atoi() at all? You are writing C++ code, you should C++ semantics instead of C semantics. For example, you can use std::istringstream instead, eg:
while (getline(inFile, buffer)) {
istringstream iss(buffer);
while (iss >> size) {
cout << size << " ";
}
cout << "~~~~~~~~~" << endl;
}
As always, there are many possible solutions. I would like to show an additional one. This is using more modern C++ elements, mainly from the algorithm and iterator library.
So, what will we do?
First we read each line as a std::string in a simple for loop with std::getline. Then we will put the line again in a std::istringstream so that we can take advantage of C++ iterator: std::istream_iterator.
This iterator will iterate over the elements in the string and extract all integers. It is like calling the extractor operator ( >> ) for all elements in the line string.
We use the iterator in the so called range constructor of os a std::vector. This inplace created vector, will be added to the destiantion data. So, as a result, we will get vector of vector of int: A 2-dimensional vector.
For debug purposes, we copy each row of intes to std::cout.
Please note that we do really need only very few and very simple statements to fulfill the task.
Please check.
#include <iostream>
#include <string>
#include <algorithm>
#include <sstream>
#include <vector>
#include <iterator>
std::istringstream sourceFile{R"(8 4 4 6 1
8 4 4 6 2
8 4 4 6 3
8 4 4 6 4
8 4 4 6 5
8 4 4 6 6
8 4 4 6 7
8 4 4 6 8
11 4 4 6 3
15 11 13
7 2 1 4 4
9 4 3 9 9
8 2 1 5 4
10 1 2 3 4 6 1
6 1 1 2 5 3 2
13 1 1 2 10 3 8
11 2 11 10 7)"};
int main()
{
// Here we will store the resulting int values
std::vector<std::vector<int>> data{};
for (std::string line{}; std::getline(sourceFile, line); ) {
// Split the line into integers and add to target array
std::istringstream iss(line);
data.emplace_back(std::vector<int>(std::istream_iterator<int>(iss), {}));
}
// Now all data is in our vector of vector of int
// Show read data on screen
std::for_each(data.begin(), data.end(), [](const std::vector<int>& v){
std::copy(v.begin(), v.end(), std::ostream_iterator<int>(std::cout, " ")); std::cout << "\n";});
return 0;
}
Please note. I do not have files on SO. So I used a std::istringstream as input stream. You may of course exchange it with any other std::ftream
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I'm trying to read in from a text file in C++ for a Testing Harness. The idea is that I have to read in the 5 values of dice and put it into an array, and then read in a string, run through the program, then read in 5 more values of dice and put those into an array, and then read in a string, and run the program, etc.
The text file looks like this:
1 1 2 1 1 Aces
2 2 4 5 6 Twos
3 3 3 2 2 FullHouse
1 2 3 4 4 SmallStraight
2 3 4 5 6 LargeStraight
6 6 6 6 6 Sixes
What would be the best way using ifstream to search the file for 1 1 2 1 1 and put those values into an array, and then read in "Aces" into a string, and then go to the next line and do the same with the values 2 2 4 5 6 and the string "Twos."
One possible and also C++-style and object oriented approach is, to put the data and operations on the data in a tiny claas.
So let's create a small struct containing an array with 5 integers and a std::string.
For that class, we additionally overwrite the 'inserter' and 'extractor' operator. Then we can use this class for input and output in the same way like for an integral data type.
The inserter operator is ultra simple an just puts the 5 integers and the text in an std:ostream. The exteractor operator is some lines more and basically works like this:
Read a complete line with std::getline
Put the read line in an std::istringstream. With that we can easily extract further data
Then we use the std::istream_iterator and copy exact 5 integers from the std::istringstream. And at the end, we read the text.
This is overall not so complicated.
Then, we can simply call in main the standard IO mechanisms.
Please see the example below:
#include <iostream>
#include <sstream>
#include <iterator>
#include <string>
#include <array>
#include <algorithm>
std::istringstream sourceFile{R"(1 1 2 1 1 Aces
2 2 4 5 6 Twos
3 3 3 2 2 FullHouse
1 2 3 4 4 SmallStraight
2 3 4 5 6 LargeStraight
6 6 6 6 6 Sixes)"
};
constexpr size_t MaxValues = 5U;
// Proxy class for reading one line of given format
struct PData {
// The Array for the values
std::array<int, MaxValues> values{};
// The description
std::string text{};
// Overwrite extractor operator
friend std::istream& operator >> (std::istream& is, PData& pdata) {
// Read complete line
std::string line{};
if (std::getline(is, line)) {
// Put line in istringstream
std::istringstream iss(line);
// Extract all integers
std::copy_n(std::istream_iterator<int>(iss), MaxValues, pdata.values.begin());
// Read the text
iss >> pdata.text;
}
return is;
}
// Overwrite inserter operator
friend std::ostream& operator << (std::ostream& os, const PData& pdata) {
std::copy_n(pdata.values.begin(), 5, std::ostream_iterator<int>(os, "\n"));
return os << pdata.text << "\n";
}
};
int main() {
PData p{};
// Read lines and split them
while (sourceFile >> p) {
// Some debug output (Not necessary)
std::cout << p << "\n\n";
// Now do with p whatever you want
}
return 0;
}
Please note: Since I do have no files on SO, I use the std::istringstream as input file. You can of course use any other std::ifstream.
I just thought I would help you out and give you the entire solution. You remind me of myself back when I was just starting out. I've put in some comments as well.
You can read more about c++ file handling here.
#include <iostream>
#include <string>
#include <vector>
#include <fstream>
// Struct to hold each "line" of the data.
struct Info {
static const size_t DICE_LENGTH = 5;
int dice_values[DICE_LENGTH];
std::string description;
};
/**
* #brief Creates the sample file (assuming it doesn't already exist)
*/
void createFile() {
std::ofstream file ("file.txt");
if (file.is_open()) {
file << "1 1 2 1 1 Aces\n";
file << "2 2 4 5 6 Twos\n";
file << "3 3 3 2 2 FullHouse\n";
file << "1 2 3 4 4 SmallStraight\n";
file << "2 3 4 5 6 LargeStraight\n";
file << "6 6 6 6 6 Sixes";
}
else {
throw "Error creating file";
}
}
int main()
{
createFile();
std::vector<Info> data;
std::ifstream file("file.txt");
if (file.is_open()) {
Info info;
while (!file.eof()) {
// read all the dice values (at most = DICE_LENGTH)
for (size_t i = 0; i < Info::DICE_LENGTH; ++i) {
file >> info.dice_values[i];
}
// read the String
std::getline(file, info.description);
data.push_back(info);
}
}
else {
std::cerr << "Error opening the file for reading.\n";
return 1;
}
// display the data the was read from the file.
for (const auto &d : data) {
// Dice values.
for (const auto &dice : d.dice_values) {
std::cout << dice << " ";
}
// String value.
std::cout << d.description << std::endl;
}
return 0;
}
Output:
1 1 2 1 1 Aces
2 2 4 5 6 Twos
3 3 3 2 2 FullHouse
1 2 3 4 4 SmallStraight
2 3 4 5 6 LargeStraight
6 6 6 6 6 Sixes
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I've got a text file which contains several lines of integers, each integer is separated by a space, I want to read these integers into an array, where each new line is the first dimension of the array, and every integer on that line is saved into the second dimension.
My text file looks something like this:
0 1 2 3 4 5 6 7 8 9
9 0 1 2 3 4 5 6 7 8
8 9 0 1 2 3 4 5 6 7
7 8 9 0 1 2 3 4 5 6
6 7 8 9 0 1 2 3 4 5
5 6 7 8 9 0 1 2 3 4
4 5 6 7 8 9 0 1 2 3
3 4 5 6 7 8 9 0 1 2
2 3 4 5 6 7 8 9 0 1
So here's what i tried so far, but it looks like a mess
string array[30][30]; //row, column
ifstream myfile("numbers.txt");
int row = 0;
int col = 0;
while(!myfile.eof())
{
//Extract columns
while(getline(myfile, array[row][col]),!'\n')
{
getline(myfile,array[row][col],' ');
col++;
}
//Extract rows
// getline(myfile,array[row][col],'\n');
// row++;
cout<< row << '\t' << array[row][col] << "\n";
}
while(!myfile.eof()) is rarely a good idea. When you've read your last line, that condition will still evaluate to true. eof() will only be set once you've tried to read beyond the last character in the file. Also, string array[30][30] is a hardcoded 30x30 C style array that doesn't fit your data. Instead, use the C++ container std::vector (that can be nested in as many dimensions as you'd like) to dynamically add numbers.
Assuming that you don't have blank lines in numbers.txt you could do like this:
#include <fstream>
#include <iostream>
#include <sstream>
#include <vector>
#include <stdexcept>
std::vector<std::vector<int>> get_2d_array_of_ints_from_stream(std::istream& is) {
std::vector<std::vector<int>> return_value;
std::string line;
while(std::getline(is, line)) { // if this fails, EOF was found or there was an error
std::istringstream iss(line); // put the line in a stringstream to extract numbers
int value; // temporary used for extraction
std::vector<int> line_values; // all values on this line
while(iss >> value) // extract like when reading an int from std::cin
line_values.push_back(value); // put the value in the 1D (line) vector
// check that all lines have the same amount of numbers
if(return_value.size() && return_value[0].size()!=line_values.size())
throw std::runtime_error("file format error");
return_value.emplace_back(std::move(line_values)); // move this line's vector<int>
// to the result_value
}
return return_value;
}
int main() {
if(std::ifstream is{"numbers.txt"}; is) {
try {
// auto arr2d = get_2d_array_of_ints_from_stream(is);
// would be the same as:
std::vector<std::vector<int>> arr2d = get_2d_array_of_ints_from_stream(is);
std::cout << "Got a " << arr2d[0].size() << "x" << arr2d.size() << " array\n";
for(const std::vector<int>& line_values : arr2d) {
for(int value : line_values) {
std::cout << " " << value;
}
std::cout << "\n";
}
std::cout << "--\n";
// or you can use the subscript style of arrays
for(size_t y = 0; y < arr2d.size(); ++y) {
for(size_t x = 0; x < arr2d[y].size(); ++x) {
std::cout << " " << arr2d[y][x];
}
std::cout << "\n";
}
} catch(const std::exception& ex) {
std::cerr << "Exception: " << ex.what() << "\n";
}
}
}
I want to read a text file line by line (I do not have many integers in each line). I want to sort each line and put them into a vector of a vector. The problem is I cannot insert them into vector line by line. I cannot let them stop at the end of the line. This is what I have now. Can anyone help me?
For example, my text file like this:
1 5 3 7 29 17
2 6 9 3 10
3 89 54 67 34
I want my output like this:
1: 1 3 5 7 17 29
2: 2 3 6 9 10
3: 3 34 54 67 89
vector<int> v;
vector<vector<int>> G_AL;
if(line!=0){ // Build matrics
string lines;
while (getline(fin, lines)) {
istringstream os(lines);
float temp;
while(os >> temp ) {
if(temp != '\n') {
v.push_back(temp);
sort(v.begin(), v.end());
// get v
}
else
{
}
G_AL.push_back(v);
}
}
}
Try this:
std::stringstream fin("2 1 3\n4 6 5\n10 9 7 8"); // Test data
std::vector<std::vector<int>> G_AL;
std::string lines;
while (getline(fin, lines)) {
std::istringstream os(lines);
std::vector<int> v;
float temp;
while(os >> temp)
v.push_back(temp);
sort(v.begin(), v.end());
G_AL.push_back(v);
}
for (size_t i=0; i<G_AL.size(); ++i)
{
std::cout << i+1 << ": ";
for (auto const & v : G_AL[i])
std::cout << v << " ";
std::cout << std::endl;
}
There are some problems in the code you provided:
The v vector is declared outside of the loop, so the values keeps accumulating every line since v is not cleared. Declaring it inside the loop fixes the problem and avoid having to clear it.
The sort can be done only once we finished reading the line.
You push the v vector into G_AL after ever value instead of after every line.
You compare a float with a character (\n), which doesn't work. In fact, the line os >> temp will evaluate to false if there is no floating point value to read, so there is no need to test once more for the end of the stream.
As title, I am a beginner in learning C++.
I want to read several sequences(s1,s2,s3...) containing integers seperated by spaces into an array,and stop reading s1 to read s2 by pressing "enter".
#
Here's the test data:
4 9 6 6
1 2 3 4
3 3 5 6 9 15 18 15 18 30 3 3 5 6 9 15 18 15 18 30 1 9 9 25 36
The result I expect would be :
arr[0]={4,9,6,6}
arr[1]={1,2,3,4}
arr[2]={3,3,5,6,9,15,18,15,18,30,3,3,5,6,9,15,18,15,18,30,1,9,9,25,36}
#
I used a time consuming way to read data into my array:
while(1){
int i=0,j=0;
int arr[100][25];
char test;
while(1){
stringstream ss;
cin.get(test);
if(test==' '){
ss<<seq;
seq.clear();
ss>>arr[i][j];
j++;
continue;
}
else if(test=='\n'){
ss<<seq;
seq.clear();
ss>>arr[i][j];
i++;
j=0;
break;
}
else{
seq=seq+test;
}
}
}
Online Judge will show "TLE" when the program reads big integers.
I know that break down integers into characters is a time consuming work,
what can I do with my program?
One way to do this could be using strings. The example below, based on this answer, reads each line in a string, and splits it by space. It will work only if the numbers are split by single spaces. The split numbers are stored in a vector of strings in the example, and can be converted to int using stoi.
string nums;
while(getline(cin,nums)) {
istringstream iss(nums);
vector<string> tokens;
copy(istream_iterator<string>(iss),
istream_iterator<string>(),
back_inserter(tokens));
// print what is added
for(int i = 0; i < tokens.size(); i++) {
cout << tokens[i] << " ";
}
cout << endl;
}