We know to read from an input stream, we can use the below standard C++ function
istream& getline (char* s, streamsize n, char delim );
However we can only provide delimiter of one byte/char.
How should I do if I wish to use delimiter with multiple bytes?
Is there any neat stuff I can leverage, boost?
Bests,
Lyn
I think you can use cin.get() instead of cin.getline(). Read one character each time and test whether the delimiter occurs.
int main(void){
string str;
int length_of_delimiter = 3;
const char *delimiter = "ABC";
char temp = '0';
bool over = false;
cout<<"Enter the stream"<<endl;
temp = cin.get();
int i = 0;
while(over == false){
for(i = 0; temp == delimiter[i] && i < length_of_delimiter; i++){
str += temp;
temp = cin.get();
}
if(i == length_of_delimiter){
//chop off the delimiter
str.erase(str.end() - length_of_delimiter, str.end());
over = true;
}
else {
str += temp;
temp = cin.get();
}
}
cout<<"The stream we wanted is: "<<str<<endl;
return 0;
}
Related
A C++ program which read data from a text file. Suppose text file contains a
paragraph about any topic. Your program asks user to enter file name without extension. Now, a
user defined function (name: ReadWordByWord()) reads all data word by word and store in a
character type array with dynamically grows according to the data.
Finally, declare a user-defined function (name: SaveInReverse()) which stores this text into a
text file (name is entered by user) in reverse order of words e.g. last words will be stored at start,
then 2nd last word, 3rd last word etc. of the original document.
And here is what I've done so far... Here I am not using the delete command, that if I use will cause an error- a heap error. How can I accomplish that first? And then what are any tips to improve this program.
#include<iostream>
#include<string>
#include<fstream>
using namespace std;
char* readWordByWord(char * old)
{
int coun = 0;
for (int i = 0; old[i] != '\0'; i++) // to find the length of word
{
coun++;
}
char *newArr = new char[coun + 1];
strcpy(newArr, old);
//delete[]old; // this is where i am putting delete command to delete the previous i.e old array and then return the new one
return newArr;
}
int size = 100;
int main()
{
fstream fin;
string forCopy[1000];
int index = 0;
fin.open("file.txt");
char *p = new char[size];
while (fin >> p)
{
p = readWordByWord(p);
//cout << p<<endl;
forCopy[index++] = p;
/*for (int i = 0; p[i] != '\0'; i++)
{
}*/
}
for (int i = index - 1; i > 0; i--)
cout << forCopy[i] << " ";
delete[]p;
p = NULL;
fin.close();
return 0;
}
I've made it from start again (must not include newlines since only a paragraph required):
#include <iostream>
#include <fstream>
#include <string>
void reverse(char *begin, char *end) { // reverses a word
char temp;
while (begin < end) {
temp = *begin;
*begin++ = *end;
*end-- = temp;
}
}
void reverseParagraph(char *arg) { // reverses each word of the paragraph
char *word_begin = arg;
char *temp = arg;
while (*temp) {
temp++;
if (*temp == '\0')
reverse(word_begin, temp - 1);
else if (*temp == ' ') {
reverse(word_begin, temp - 1);
word_begin = temp + 1;
}
}
reverse(arg, temp - 1);
}
int main() {
std::ifstream file("file.txt");
std::string fileData = "";
while(getline(file, fileData)); // counting the number of letters for memory allocation
size_t len = fileData.length();
char *str = new char[len + 1];
strcpy(str, fileData.c_str());
reverseParagraph(str); // reverse the entire character pointer
std::cout << str << std::endl; // displays for testing
std::ofstream fileOut("out.txt");
fileOut << str << std::endl; // saving the output into another file
fileOut.close();
delete[] str;
file.close();
return 0;
}
This program firstly gets the containing data of a file and then assigns into a variable. The variable is then converted into character (pointer) after getting the string length.
After that, it recursively reverses the position each word of the fileData and finally it displays. The modified data is thereafter printed into another file.
sorry for such a stupid question but I couldn't find any obvious answer.
I need to read from stdin first an int n with the size of an array, and then integer values from a string in the format "1 2 3 4 5 6" with n elements.
If I knew the number of parameters at compile time I could use something like a scanf (or the safe alternatives) with a format string like "%d %d %d %d %d %d", but here I will only know that value at run time.
What would be the best way to do this in C++? Performance is important but more than that safety.
How should I read a format string of variable length in C++ from stdin?
You should not attempt to do such thing. Only ever use constant format strings.
I need to read from stdin first an int n with the size of an array, and then integer values
What would be the best way to do this in C++?
Read one value at a time. Repeat using a loop.
Here's a function that does what errorika describes:
const int SIZE = //as much of your memory as you'd like the user to have access to
***caller function must include this:
//allocate a string to hold some data;
char* buffer = NULL;
buffer = malloc (SIZE * sizeof(char));
if (buffer == NULL) {
printf("malloc error terminating\n");
return;
}
***
void getEntry(char* buffer) {
int count = 0;
int maxlen = SIZE - 1;
char a = '0';
for (int i = 0; i < SIZE; i++) {
buffer[i] = '0';
}
while (a != '\n' && count < maxlen) {
a = fgetc(stdin);
buffer[count] = a;
count++;
}
if (a == '\n') {
buffer[count - 1] = '\0';
}
else {
buffer[count] = '\0';
do {
a = fgetc(stdin);
} while (a != '\n');
}
}
This is all basic C code but user entry is evil. Here is what I've come up with for more C++ idiomatic user input functions (query is just the message string you pass in):
template<typename T>
void getInput(const std::string query, T& entry) {
std::string input;
std::cout << query << std::endl;
getline(std::cin, input);
std::stringstream buffer{input};
buffer >> entry;
}
OR
template<typename T>
void getInput2(std::string query, T& entry) {
bool validInput = false;
while (validInput == false)
{
validInput = true;
std::cout << query << std::endl;
std::cin >> entry;
if (std::cin.fail()) {
validInput = false;
std::cout << "Unacceptable entry\n" << std::endl;
}
std::cin.clear();
std::cin.ignore(std::numeric_limits<std::streamsize>::max(), '\n');
}
}
I am trying to match words from user input with a string from a text file.
When this code runs, it crashes after the file is opened. (marked by ****)
How can I change it to properly match the strings from user input with strings from the text file.
Any help would be appreciated, thank you.
const int Size = 81; // 80 characters for the line + 1 for the '\0'
const int MaxNumberOfWords = 10;
int main() {
char input[81], temp[81], fin[81];
printf("Input a string\n");
fgets(input, 81, stdin);
int len = strlen(input);
char *div;
div = strtok(input, " ");
while (div != NULL) {
printf("%s\n",div);
div = strtok(NULL, " ");
ifstream inStream; // declare an input stream for my use
char theWords[ MaxNumberOfWords][ Size]; // Array to store words from input line
int wordRow = 0; // Row for the current word
char wordToLookup[ Size]; // word to lookup
bool wordWasFound = false; // flag to track whether or not word is found
char c; // stores return character after input
inStream.open( "C:\\Users\\dqiao4\\Desktop\\Dev-Cpp\\dictionaryMax6.txt");
assert( ! inStream.fail() ); // make sure file open was OK
//*****this is where the code crashes
while ( inStream >> theWords[ wordRow]) {
wordRow++;
}
for (int i=0; i<wordRow; i++) {
// See if this word matches
if ( strcmp( div, theWords[ i]) == 0 ){
wordWasFound = true;
break; // quit looking
}
}
}
}
int main() {
char input[81];int i=0,j=0,k=0;
cout<<"Input a string ";
while(i<=80){
input[i]=getch();
cout<<input[i];
if(input[i]=='.')
break;
i++;
}
ifstream File("C:\\User\\New.txt");
string line;
if(File)
{
while(getline(File, line))
{
char buff[1024];
strcpy(buff, line.c_str());
while(j<35){
k=0;
while(k<i){
if(buff[j]==input[k])
{
int j1=j,k1=k;
while(true){
if(buff[j1]==input[k1])
{
if(input[j1]=='.'){
cout<<"match";
return 0;
}
j1++;k1++;
}
else
break;
}
}k++;
}j++;
cout<<endl;
}
}
}
}
#inlude <sstream>
#include <string>
in your source and read the text file in string stream buffer, convert it to string and do
auto pos = file_in_str.find("word_to_find");
That pos is the the starting index of word in file
I have written a program to concatenate two strings without using strcat using two while loops for beginners. Need your suggestion to code it with one loop. Kindly share your logic thanks
char first[1000];
char second[2000];
char result[4000];
void concat(char *first, char *second, char *result){
int str_selector = 0;
int i = 0, result_pos = 0;
char *current_str = first;
while(1){
if(str_selector == 1 && current_str[i] == '\0'){
result[result_pos] = '\0';
break;
}
if(str_selector == 0)
current_str = first;
else
current_str = second;
if(current_str[i] != '\0'){
result[result_pos] = current_str[i];
result_pos++;
i++;
}
else{
i = 0;
str_selector = 1;
}
}
}
I have this function sentanceParse with a string input which returns a list. The input might be something like "Hello my name is Anton. What's your name?" and then the return value would be a list containing "Hello my name is Anton" and "What's your name?". However, this is not what happens. It seems as if the whitespaces in the sentences are treated like a separator and therefore the return is rather "Hello", "my", "name" etc instead of what I expected.
How would you propose I solve this?
As I am not a 100% sure the problem does not lie within my code, I will add that to the post as well:
Main:
list<string> mylist = sentanceParse(textCipher);
list<string>::iterator it;
for(it = mylist.begin(); it != mylist.end(); it++){
textCipher = *it;
cout << textCipher << endl; //This prints out the words separately instead of the entire sentances.
sentanceParse:
list<string> sentanceParse(string strParse){
list<string> strList;
int len = strParse.length();
int pos = 0;
int count = 0;
for(int i = 0; i < len; i++){
if(strParse.at(i) == '.' || strParse.at(i) == '!' || strParse.at(i) == '?'){
if(i < strParse.length() - 1){
while(i < strParse.length() - 1 && (strParse.at(i+1) == '.' || strParse.at(i+1) == '!' || strParse.at(i+1) == '?')){
if(strParse.at(i+1) == '?'){
strParse.replace(i, 1, "?");
}
strParse.erase(i+1, 1);
len -= 1;
}
}
char strTemp[2000];
int lenTemp = strParse.copy(strTemp, i - pos + 1, pos);
strTemp[lenTemp] = '\0';
std::string strAdd(strTemp);
strList.push_back(strAdd);
pos = i + 1;
count ++;
}
}
if(count == 0){
strList.push_back(strParse);
}
return strList;
}
Your implementation of sentence parse is wrong, here is a simpler correct solution.
std::list<std::string> sentence_parse(const std::string &str){
std::string temp;
std::list<std::string> t;
for(int x=0; x<str.size();++x){
if(str[x]=='.'||str[x]=='!'||str[x]=='?'){
if(temp!="")t.push_back(temp);//Handle special case of input with
//multiple punctuation Ex. Hi!!!!
temp="";
}else temp+=str[x];
}
return t;
}
EDIT:
Here is a full example program using this function. Type some sentences in your console, press enter and it will spit the sentences out with a newline separating them instead of punctuation.
#include <iostream>
#include <string>
#include <list>
std::list<std::string> sentence_parse(const std::string &str){
std::string temp;
std::list<std::string> t;
for(int x=0; x<str.size();++x){
if(str[x]=='.'||str[x]=='!'||str[x]=='?'){
if(temp!="")t.push_back(temp);//Handle special case of input with
//multiple punctuation Ex. Hi!!!!
temp="";
}else temp+=str[x];
}
return t;
}
int main (int argc, const char * argv[])
{
std::string s;
while (std::getline(std::cin,s)) {
std::list<std::string> t= sentence_parse(s);
std::list<std::string>::iterator x=t.begin();
while (x!=t.end()) {
std::cout<<*x<<"\n";
++x;
}
}
return 0;
}
// This function should be easy to adapt to any basic libary
// this is in Windows MFC
// pass in a string, a char and a stringarray
// returns an array of strings using char as the separator
void tokenizeString(CString theString, TCHAR theToken, CStringArray *theParameters)
{
CString temp = "";
int i = 0;
for(i = 0; i < theString.GetLength(); i++ )
{
if (theString.GetAt(i) != theToken)
{
temp += theString.GetAt(i);
}
else
{
theParameters->Add(temp);
temp = "";
}
if(i == theString.GetLength()-1)
theParameters->Add(temp);
}
}