This code is supposed to make a array of strings, randomly order them, and then print the order. Unfortunately it adds a blank line in one of the spaces ( i think this is getline's doing). Any ideas how to fix that? I tried setting array [0] = NULL; it complains about operators...
#include <iostream>
#include <stdio.h>
#include <conio.h>
#include <time.h>
#include <string>
#include <cstdlib>
using std::cout;
using std::endl;
using namespace std;
void swap (string &one, string &two)
{
string tmp = one;
one = two;
two = tmp;
}
int rand_loc (int size)
{
return (rand() % size);
}
int main()
{
srand(time(NULL));
int size;
cin >> size;
string *array = new string[size];
//array[0] = NULL ;
for (int x = 0; x < size; x++)
{
getline(cin, array[x]);
}
//for (int x = 0; x < size; x++)
//{
// swap (array[rand_loc(size)], array[rand_loc(size)]);
//}
cout << endl;
for (int x = 0; x < size; x++)
{
//out << array[x] << endl;
int y = x + 1;
cout<<y<<"."<<" "<<array[x]<<endl;
}
delete[] array;
}
The first call to getline() will immediately hit the newline that the user entered after inputting size, and will therefore return an empty string. Try to call cin.ignore(255, '\n'); before the first call to getline(). This will skip up to 255 (an arbitrarily selected number) characters until a \n is encountered (and the newline will be skipped as well).
Edit: As #Johnsyweb and #ildjarn point out, std::numeric_limits<streamsize>::max() is a much better choice than 255.
Related
I have a task where i need to revert a list of variable length numbers. This could be "1 2 3" or "5 6 7 8 9 10".
The sorting itself works fine.
But I can't figure out how to read the user input (with variable length) and then only execute the reverseSort once.
How can I read the user input into an array where each index is based on the space between the numbers?
Here is my code:
#include <iostream>
#include <string>
using namespace std;
bool sorted = true;
int temp;
int * arr;
int arrLength = 5;
int arrs;
// int arr = {1,2,3,4,5};
void reverseSort(int arr[], int n){
sorted = true;
for (int i = 0; i < n-1; i++){
if (arr[(i + 1)] > arr[i]){
temp = arr[i];
arr[i] = arr[i+1];
arr[i+1] = temp;
sorted = false;
}
}
if (!sorted){
reverseSort(arr,n);
}
}
int main(void){
// get user input !?!?!?!?!
cin >> arrs;
cout << arrs;
reverseSort(arr,arrLength);
for (int i = 0; i < arrLength; i++){
std::cout << arr[i] << " ";
}
return 0;
}
If you don't know number of inputs you need struct that can be resized. std::vector is good for it. For adding new data you can use member function push_back.
You can read the input line as std::string (by std::getline) and you can open new stream with read data (std::istringstream). Further one can read values from new stream.
And I think you can use std::sort instead of reverseSort (but for 'reverse' you need use std::greater as comparator).
#include <vector>
#include <iostream>
#include <fstream>
#include <sstream>
#include <string>
#include <algorithm>
int main(void){
std::vector<int> arrs;
// read only one line
std::string input;
std::getline(std::cin, input);
std::istringstream row(input);
int x;
while (row >> x)
{
arrs.push_back(x);
}
//like your reverseSort
std::sort(arrs.begin(), arrs.end(), std::greater<int>{});
for (auto var : arrs) {
std::cout << var << "; ";
}
return 0;
}
I'm trying to figure it out why this code doesn't work as it should. I would like to allocate memory for a dictionary file with over 250,000 words. Memory allocation works OK. However free memory doesn't. And, honestly I don't know why. It breaks during deallocation. Below is the code.
Thank you.
#include <iostream> // For general IO
#include <fstream> // For file input and output
#include <cassert> // For the assert statement
using namespace std;
const int NumberOfWords = 500000; // Number of dictionary words
//if i change to == to exact number of words also doesnt work
const int WordLength = 17; // Max word size + 1 for null
void allocateArray(char ** & matrix){
matrix = new char*[NumberOfWords];
for (int i = 0; i < NumberOfWords; i++) {
matrix[i] = new char[WordLength];
// just to be safe, initialize C-string to all null characters
for (int j = 0; j < WordLength; j++) {
matrix[i][j] = NULL;
}//end for (int j=0...
}//end for (int i...
}//end allocateArray()
void deallocateArray(char ** & matrix){
// Deallocate dynamically allocated space for the array
for (int i = 0; i < NumberOfWords; i++) {
delete[] matrix[i];
}
delete[] matrix; // delete the array at the outermost level
}
int main(){
char ** dictionary;
// allocate memory
allocateArray(dictionary);
// Now read the words from the dictionary
ifstream inStream; // declare an input stream for my use
int wordRow = 0; // Row for the current word
inStream.open("dictionary.txt");
assert(!inStream.fail()); // make sure file open was OK
// Keep repeating while input from the file yields a word
while (inStream >> dictionary[wordRow]) {
wordRow++;
}
cout << wordRow << " words were read in." << endl;
cout << "Enter an array index number from which to display a word: ";
long index;
cin >> index;
// Display the word at that memory address
cout << dictionary[index] << endl;
deallocateArray(dictionary);
return 0;
}
The problem is in the following line:
while (inStream >> dictionary[wordRow]) {
There is no limit on the input line length and the application overwrites at least one of string buffers. I would fix it this way:
while (inStream >> std::setw(WordLength - 1) >> dictionary[wordRow]) {
Please do not forget to add
#include <iomanip>
with setd::setw declaration
I have to write a short routine that will write out only upper case letters in reversed order. I managed to muster up code that somehow works, but whenever I test out my code with one specific input:
7 ENTER a b C d E f G
Instead of getting G E C I get
G (special) r E
I can't see what causes the problem, especially because it works for so many other cases. Here's the code:
#include <iostream>
using namespace std;
int main() {
int n;
cin >> n;
char stringa[n];
int length = 0;
for (int i = 0; i <= n-1; i++) {
char letter;
cin >> letter;
if (isupper (letter)) {
stringa[((n-i) - 1)] = letter;
length = length +1;
} } for ( int i =0; i<=length-1; i++) {
cout << ciag[i]
The main problem is that you are not populating your array correctly.
You are not initializing the content of the array before filling it, so it contains random garbage. Then you are filling specific elements of the array using indexes that are the directly related to each uppercase character's original position in the input, rather than the position they should appear in the output.
Since you are not initializing the array, and the input has mixed lower/upper casing, your array is going to have gaps containing random data:
stringa[0] = G
stringa[1] = <random>
stringa[2] = <random>
stringa[3] = <random>
stringa[4] = E
stringa[5] = <random>
stringa[6] = <random>
stringa[7] = <random>
stringa[8] = C
stringa[9] = <random>
stringa[10] = <random>
stringa[11] = <random>
stringa[12] = <random>
stringa[13] = <random>
stringa[14] = R
stringa[15] = E
stringa[16] = T
stringa[17] = N
stringa[18] = E
stringa[19] = <random>
stringa[20] = <random>
That is what you are seeing appear in your garbled output.
Try something more like this instead:
#include <iostream>
#include <vector>
#include <cctype>
int main()
{
int n;
std::cin >> n;
std::vector<char> stringa(n); // 'char stringa[n];' is not standard!
int length = 0;
for (int i = 0; i < n; ++i)
{
char letter;
std::cin >> letter;
if (std::isupper (letter))
{
stringa[length] = letter;
++length;
}
}
for (int i = length-1; i >= 0; --i)
{
std::cout << stringa[i];
}
return 0;
}
Or:
#include <iostream>
#include <vector>
#include <algorithm>
#include <cctype>
int main()
{
int n;
std::cin >> n;
std::vector<char> stringa(n); // 'char stringa[n];' is not standard!
int length = 0;
for (int i = 0; i < n; ++i)
{
char letter;
std::cin >> letter;
if (std::isupper (letter))
{
stringa[length] = letter;
++length;
}
}
std::reverse(stringa.begin(), stringa.begin()+length);
for (int i = 0; i < length; ++i)
{
std::cout << stringa[i];
}
return 0;
}
Both approaches produces the following array content during the first loop, and then simply output it in reverse order in the second loop:
stringa[0] = E
stringa[1] = N
stringa[2] = T
stringa[3] = E
stringa[4] = R
stringa[5] = C
stringa[6] = E
stringa[7] = G
Alternatively, I would suggest using std::getline() instead of a reading loop to obtain the user's input, and then simply manipulate the resulting std::string as needed:
#include <iostream>
#include <string>
#include <algorithm>
bool IsNotUpper(char ch)
{
return !std::isupper(ch);
}
int main()
{
std::string stringa;
std::getline(std::cin, stringa); // returns "7 ENTER a b C d E f G"
// so std::isupper() will return false for everything not in A-Z
std::setlocale(LC_ALL, "C");
stringa.erase(
std::remove_if(stringa.begin(), stringa.end(), &IsNotUpper),
stringa.end());
// returns "ENTERCEG"
std::reverse(stringa.begin(), stringa.end());
// returns "GECRETNE"
std::cout << stringa;
return 0;
}
Or, if using C++11 and later, you can use a lambda instead of a function for the std::remove_if() predicate:
#include <iostream>
#include <string>
#include <algorithm>
int main()
{
std::string stringa;
std::getline(std::cin, stringa);
std::setlocale(LC_ALL, "C");
stringa.erase(
std::remove_if(
stringa.begin(), stringa.end(),
[](char ch){return !std::isupper(ch);}
),
stringa.end());
std::reverse(stringa.begin(), stringa.end());
std::cout << stringa;
return 0;
}
Your algorithm just doesn't make any sense. You are expecting the characters to be in the array with no gaps but you skip an entry in the array when the input isn't a capital letter. Instead, put the capital letters in consecutive slots in the array in the forward direction and then traverse it in reverse order afterwards.
Currently I am getting an runtime "assertation error"
Here is the error:
I'm reading words from a text file into dynamically allocated arrays.
this block of code is where I am filling the new arrays.
I know the problem is being caused by this block of code and something about my logic is off just can't see what it is.
//fill new arrays
for( int y = 0; y < new_numwords; y++)
{
for( int i = 0; i < NUM_WORDS; i++)
{
if (!strcmp(SentenceArry[i], EMPTY[0]) == 0)
{
New_SentenceArry[y] = SentenceArry[i];
New_WordCount[y] = WordCount[i];
y++;
}
}
}
Also how would I pass this dynamically allocated 2D array to a function? (the code really needs to be cleaned up as a whole)
char** SentenceArry = new char*[NUM_WORDS]; //declare pointer for the sentence
for( int i = 0; i < NUM_WORDS; i++)
{
SentenceArry[i] = new char[WORD_LENGTH];
}
Here is the full extent of the code.. help would be much appreciated!
Here is what is being read in:
and the current output (the output is how it's suppose to be ):
#define _CRT_SECURE_NO_WARNINGS
#include <iostream>
#include <fstream>
#include <cstring>
#include <cctype>
#include <iomanip>
using std::setw;
using std::left;
using std::cout;
using std::cin;
using std::endl;
using std::ifstream;
int main()
{
const int NUM_WORDS = 17;//constant for the elements of arrays
const int WORD_LENGTH = 50;//constant for the length of the cstrings (NEED TO GIVE THE VALUE ZERO STILL!)
short word_entry = 0; //declare counter
short new_numwords= 0; //declare new word count
char EMPTY[1][4]; //NULL ARRAY
EMPTY[0][0] = '\0';//define it as null
char** SentenceArry = new char*[NUM_WORDS]; //declare pointer for the sentence
for( int i = 0; i < NUM_WORDS; i++)
{
SentenceArry[i] = new char[WORD_LENGTH];
}
int WordCount[NUM_WORDS];//declare integer array for the word counter
for(int i = 0; i < NUM_WORDS; i++)//fill int array
{
WordCount[i] = 1;
}
int New_WordCount[NUM_WORDS] = {0};
ifstream read_text("DataFile.txt"); //read in our text file
if (read_text.is_open()) //check if the the file was opened
{
read_text >> SentenceArry[word_entry];
//REMOVE PUNCTUATION BEFORE BEING READ INTO THE ARRAY
while (!read_text.eof())
{
word_entry++; //increment counter
read_text >> SentenceArry[word_entry]; //read in single words of the text file into the array SentenceArry
char* ptr_ch;//declare our pointer that will find chars
ptr_ch = strstr( SentenceArry[word_entry], ",");//look for "," within the array
if (ptr_ch != NULL)//if true replace it with a null character
{
strncpy( ptr_ch, "\0" , 1);
}//end if
else
{
ptr_ch = strstr( SentenceArry[word_entry], ".");//look for "." within the array
if (ptr_ch != NULL)//if true replace it with a null character
{
strncpy( ptr_ch, "\0" , 1);
}//end if
}//end else
} //end while
}//end if
else
{
cout << "The file could not be opened!" << endl;//display error message if file doesn't open
}//end else
read_text.close(); //close the text file after eof
//WORD COUNT NESTED FOR LOOP
for(int y = 0; y < NUM_WORDS; y++)
{
for(int i = y+1; i < NUM_WORDS; i++)
{
if (strcmp(SentenceArry[y], EMPTY[0]) == 0)//check if the arrays match
{
y++;
}
else
{
if (strcmp(SentenceArry[y], SentenceArry[i]) == 0)//check if the arrays match
{
WordCount[y]++;
strncpy(SentenceArry[i], "\0" , 3);
}//end if
}//end if
}//end for
}//end for
//find how many arrays still contain chars
for(int i = 0; i < NUM_WORDS; i++)
{
if (!strcmp(SentenceArry[i], EMPTY[0]) == 0)
{
new_numwords++;
}
}
//new dynamic array
char** New_SentenceArry = new char*[new_numwords]; //declare pointer for the sentence
for( int i = 0; i < new_numwords; i++)
{
New_SentenceArry[i] = new char[new_numwords];
}
//fill new arrays
for( int y = 0; y < new_numwords; y++)
{
for( int i = 0; i < NUM_WORDS; i++)
{
if (!strcmp(SentenceArry[i], EMPTY[0]) == 0)
{
New_SentenceArry[y] = SentenceArry[i];
New_WordCount[y] = WordCount[i];
y++;
}
}
}
//DISPLAY REPORT
cout << left << setw(15) << "Words" << left << setw(9) << "Frequency" << endl;
for(int i = 0; i < new_numwords; i++) //compare i to the array constant NUM_WORDS
{
cout << left << setw(15) << New_SentenceArry[i] << left << setw(9) << New_WordCount[i] << endl; //display the contents of the array SentenceArry
}
//DEALLOCATION
for( int i = 0; i < NUM_WORDS; i++)//deallocate the words inside the arrays
{
delete [] SentenceArry[i];
}
for(int i = 0; i < new_numwords; i++)
{
delete [] New_SentenceArry[i];
}
delete [] SentenceArry; //deallocate the memory allocation made for the array SentenceArry
delete [] New_SentenceArry;//deallocate the memory allocation made for the array New_SentenceArry
}//end main
There are several issues with the code, not withstanding that this could be written using C++, not C with a sprinkling of C++ I/O..
Issue 1:
Since you're using c-style strings, any copying of string data will require function calls such as strcpy(), strncpy(), etc. You failed in following this advice in this code:
for( int y = 0; y < new_numwords; y++)
{
for( int i = 0; i < NUM_WORDS; i++)
{
if (!strcmp(SentenceArry[i], EMPTY[0]) == 0)
{
New_SentenceArry[y] = SentenceArry[i]; // This is wrong
New_WordCount[y] = WordCount[i];
y++;
}
}
}
You should be using strcpy(), not = to copy strings.
strcpy(New_SentenceArry[y], SentenceArry[i]);
Issue 2:
You should allocate WORD_LENGTH for both the original and new arrays. The length of the strings is independent of the number of strings.
char** New_SentenceArry = new char*[new_numwords]; //declare pointer for the sentence
for( int i = 0; i < new_numwords; i++)
{
New_SentenceArry[i] = new char[new_numwords];
}
This should be:
char** New_SentenceArry = new char*[new_numwords]; //declare pointer for the sentence
for( int i = 0; i < new_numwords; i++)
{
New_SentenceArry[i] = new char[WORD_LENGTH];
}
Issue 3:
Your loops do not check to see if the index is going out of bounds of your arrays.
It seems that you coded your program in accordance to the data that you're currently using, instead of writing code regardless of what the data will be. If you have limited yourself to 17 words, where is the check to see if the index goes above 16? Nowhere.
For example:
while (!read_text.eof() )
Should be:
while (!read_text.eof() && word_entry < NUM_WORDS)
Issue 4:
You don't process the first string found correctly:
read_text >> SentenceArry[word_entry]; // Here you read in the first word
while (!read_text.eof() )
{
word_entry++; //increment counter
read_text >> SentenceArry[word_entry]; // What about the first word you read in?
Summary:
Even with these changes, I can't guarantee that the program won't crash. Even it it doesn't crash with these changes, I can't guarantee it will work 100% of the time -- a guarantee would require further analysis.
The proper C++ solution, given what this assignment was about, is to use a std::map<std::string, int> to keep the word frequency. The map would automatically store similar words in one entry (given that you remove the junk from the word), and would bump up the count to 1 automatically, when the entry is inserted into the map.
Something like this:
#include <string>
#include <map>
#include <algorithm>
typedef std::map<std::string, int> StringMap;
using namespace std;
bool isCharacterGarbage(char ch)
{ return ch == ',' || ch == '.'; }
int main()
{
StringMap sentenceMap;
//...
std::string temp;
read_text >> temp;
temp.erase(std::remove_if(temp.begin(), temp.end(), isCharacterGarbage),temp.end());
sentenceMap[temp]++;
//...
}
That code alone does everything your original code did -- keep track of the strings, bumps up the word count, removes the junk characters from the word before being processed, etc. But best of all, no manual memory management. No calls to new[], delete[], nothing. The code just "works". That is effectively 5 lines of code that you would just need to write a "read" loop around.
I won't go through every detail, you can do that for yourself since the code is small, and there are vast amounts of resources available explaining std::map, remove_if(), etc.
Then printing out is merely going through the map and printing each entry (string and count). If you add the printing, that may be 4 lines of extra code. So in all, practically all of the assignment is done with effectively 10 or so lines of code.
Remove below code.
for(int i = 0; i < new_numwords; i++)
{
delete [] New_SentenceArry[i];
}
I need to traverse a file in a vertical manner. If suppose the file contents are:
adg
beh
cfi
It should print the file as:
abc
def
ghi
The length for each line will be same(i.e. all lines will be of length 3 for above example). I have written a code but it doesn't traverse the file as required.
#include<iostream>
#include<fstream>
#include<string>
using namespace std;
int main()
{
fstream fs;
fs.open("asd.txt",ios::in);
string str;
char *ch = new char();
int lineLen = 0, k = 0;
if(getline(fs,str))
{
lineLen = str.length();
}
fs.seekg(0);
if(lineLen > 0)
{
for(int i = 0;i<lineLen;i++)
{
fs.seekg(i+k*lineLen);
while(fs.read(ch,1))
{
k++;
fs.seekg(i+k*lineLen);
cout<<*ch;
}
k = 0;
}
}
fs.close();
cin.ignore();
}
I am a bit new to file handling and couldn't find the mistake. Also, is there a better approach for this to be followed?
Pretty much your way with some little tweaks
//lines = no. of lines in file
fs.seekg(0, fs.beg);
fs.clear();
if(lineLen > 0)
{
for(int k = 0; k < lineLen; k++) {
for(int i = 0;i<lines;i++){
fs.seekg(k+i * (lineLen + 2), fs.beg); //use lines + 2
if(fs.read (ch,1));
cout << *ch;
}
cout << endl;
}
Untested pseudo-code that may give you some ideas. Basically, load the whole file into a 2d vector of characters for easy access. It will use more memory than reading directly from the file but this won't matter unless the file is very big.
vector<vector<char>> filemap;
string line;
while (getline(filestream, line))
{
filemap.push_back(vector<char>(line.begin(), line.end()));
}
for (int x = 0; x < XSIZE; x++)
{
for (int y = 0; y < YSIZE; y++)
{
filestream << filemap[y][x]; // note x/y are opposite way round in 2d vectors
}
filestream << '\n';
}
You might find this task much simpler if you were to use mmap(2). There may be a C++ equivalent or wrapper, but I'm afraid I'm not much of an expert on that front. Hopefully someone will come along with a better answer if that's the case.
Here's a quick C (not ++) example. I'll see if I can google around and C++ify it some more:
#include <fcntl.h>
#include <stdio.h>
#include <string.h>
#include <sys/mman.h>
#include <sys/stat.h>
#include <unistd.h>
int main(void)
{
int fd = open("input", O_RDONLY);
struct stat s;
fstat(fd, &s);
// map the file as one big string
char *c = mmap(0, s.st_size, PROT_READ, MAP_SHARED, fd, 0);
// calculate sizes
int columns = strchr(c, '\n') - c; // first newline delimits a row
int stride = columns + 1; // count the newline!
int rows = s.st_size / stride; // all rows are the same length
for (int x = 0; x < columns; x++)
{
for (int y = 0; y < rows; y++)
{
putchar(c[y*stride + x]);
}
putchar('\n');
}
munmap(c, s.st_size);
close(fd);
return 0;
}
Edit: A quick search around didn't turn up a much better way to handle this in C++ as far as I could tell. I mean, I can add a typecast on the mmap line and change the putchar calls to std::cout, but that doesn't really seem like it makes any difference.
Instead of trying to seek() repeatedly in the source file it is much easier and faster to simply read in the whole source file then generate output from the in-memory contents.
This sounds an awful like like a class assignment, so I won't simply write the answer for you. However this should point you in the right way -- Some PseodoCode is included
To avoid pain, it should presumably be safe to assume some upper bound on line length and max lines, i.e.,
const int MaxLines = 100;
const int MaxLength = 80;
int lineno, linelength;
// array of char pointers for each line
char *lines[] = (*lines[])malloc(Maxlines * sizeof(char*));
// ReadLoop
lineno = 0;
while (not eof)
{
getline(buffer);
if (++lineno++ == 1)
{
linelength = strlen(buffer);
}
else
{
if (linelength != strlen(buffer))
{
cout "Line # " << lineno << " does not match the expected length";
exit();
}
}
lines[lineno] = malloc(strlen(buffer)+1));
strcpy(lines[lineno], buffer);
}
int cc, linecnt = lineno;
// now all data in memory, output "vertical data"
for (cc = 0; cc < linelength; ++cc)
{
for (lineno=0; lineno<<linelength; ++lineno)
{
cout << lines[xx][yy]; // xx && yy left you to figure out
}
cout "\n";
}
Provided that your file is not enormous, there's no reason not to just slurp the whole thing into memory. There may be a more idiomatic way to do this in C++, but the following works:
#include <iostream>
#include <string>
#include <fstream>
#include <vector>
int main(int argc, char *argv[])
{
std::fstream infile("foo.txt");
std::vector<std::string> lines;
std::string line;
while(std::getline(infile,line)) {
lines.push_back(line);
}
int m=lines.size();
int n=lines[0].length();
for(int i=0; i<n; i++) {
for(int j=0; j<m; j++) {
std::cout << lines[j].at(i);
}
std::cout << std::endl;
}
return 0;
}
Problems arise when all the lines in the file are not the same length, of course.
And now, a version that “doesn't use any extra memory” (of course, it does, but not much):
#include <iostream>
#include <string>
#include <fstream>
#include <vector>
#include <algorithm>
int main(int argc, char *argv[])
{
std::fstream infile("foo.txt");
std::vector<std::string> lines;
std::string line;
std::getline(infile, line);
int n = line.length();
int m = 1+std::count(std::istreambuf_iterator<char>(infile),
std::istreambuf_iterator<char>(), '\n');
infile.clear();
for(int i=0; i<n; i++) {
for(int j=0; j<m; j++) {
infile.seekg(j*m+i);
std::cout << char(infile.peek());
}
std::cout << std::endl;
}
return 0;
}