I've been looking for ways to count the number of words in a string, but specifically for strings that may contain typos (i.e. "_This_is_a___test" as opposed to "This_is_a_test"). Most of the pages I've looked at only handle single spaces.
This is actually my first time programming in C++, and I don't have much other programming experience to speak of (2 years of college in C and Java). Although what I have is functional, I'm also aware it's complex, and I'm wondering if there is a more efficient way to achieve the same results?
This is what I have currently. Before I run the string through numWords(), I run it through a trim function that removes leading whitespace, then check that there are still characters remaining.
int numWords(string str) {
int count = 1;
for (int i = 0; i < str.size(); i++) {
if (str[i] == ' ' || str[i] == '\t' || str[i] == '\n') {
bool repeat = true;
int j = 1;
while (j < (str.size() - i) && repeat) {
if (str[i + j] != ' ' && str[i + j] != '\t' && str[i + j] != '\n') {
repeat = false;
i = i + j;
count++;
}
else
j++;
}
}
}
return count;
}
Also, I wrote mine to take a string argument, but most of the examples I've seen used (char* str) instead, which I wasn't sure how to use with my input string.
You don't need all those stringstreams to count word boundary
#include <string>
#include <cctype>
int numWords(std::string str)
{
bool space = true; // not in word
int count = 0;
for(auto c:str){
if(std::isspace(c))space=true;
else{
if(space)++count;
space=false;
}
}
return count;
}
One solution is to utilize std::istringstream to count the number of words and to skip over spaces automatically.
#include <sstream>
#include <string>
#include <iostream>
int numWords(std::string str)
{
int count = 0;
std::istringstream strm(str);
std::string word;
while (strm >> word)
++count;
return count;
}
int main()
{
std::cout << numWords(" This is a test ");
}
Output:
4
Albeit as mentioned std::istringstream is more "heavier" in terms of performance than writing your own loop.
Sam's comment made me write a function that does not allocate strings for words. But just creates string_views on the input string.
#include <cassert>
#include <cctype>
#include <vector>
#include <string_view>
#include <iostream>
std::vector<std::string_view> get_words(const std::string& input)
{
std::vector<std::string_view> words;
// the first word begins at an alpha character
auto begin_of_word = std::find_if(input.begin(), input.end(), [](const char c) { return std::isalpha(c); });
auto end_of_word = input.begin();
auto end_of_input = input.end();
// parse the whole string
while (end_of_word != end_of_input)
{
// as long as you see text characters move end_of_word one back
while ((end_of_word != end_of_input) && std::isalpha(*end_of_word)) end_of_word++;
// create a string view from begin of word to end of word.
// no new string memory will be allocated
// std::vector will do some dynamic memory allocation to store string_view (metadata of word positions)
words.emplace_back(begin_of_word, end_of_word);
// then skip all non readable characters.
while ((end_of_word != end_of_input) && !std::isalpha(*end_of_word) ) end_of_word++;
// and if we haven't reached the end then we are at the beginning of a new word.
if ( end_of_word != input.end()) begin_of_word = end_of_word;
}
return words;
}
int main()
{
std::string input{ "This, this is a test!" };
auto words = get_words(input);
for (const auto& word : words)
{
std::cout << word << "\n";
}
return 0;
}
You can use standard function std::distance with std::istringstream the following way
#include <iostream>
#include <sstream>
#include <string>
#include <iterator>
int main()
{
std::string s( " This is a test" );
std::istringstream iss( s );
auto count = std::distance( std::istream_iterator<std::string>( iss ),
std::istream_iterator<std::string>() );
std::cout << count << '\n';
}
The program output is
4
If you want you can place the call of std::distance in a separate function like
#include <iostream>
#include <sstream>
#include <string>
#include <iterator>
size_t numWords( const std::string &s )
{
std::istringstream iss( s );
return std::distance( std::istream_iterator<std::string>( iss ),
std::istream_iterator<std::string>() );
}
int main()
{
std::string s( " This is a test" );
std::cout << numWords( s ) << '\n';
}
If separators can include other characters apart from white space characters as for example punctuations then you should use methods of the class std::string or std::string_view find_first_of and find_first_not_of.
Here is a demonstration program.
#include <iostream>
#include <string>
#include <string_view>
size_t numWords( const std::string_view s, std::string_view delim = " \t" )
{
size_t count = 0;
for ( std::string_view::size_type pos = 0;
( pos = s.find_first_not_of( delim, pos ) ) != std::string_view::npos;
pos = s.find_first_of( delim, pos ) )
{
++count;
}
return count;
}
int main()
{
std::string s( "Is it a test ? Yes ! Now we will run it ..." );
std::cout << numWords( s, " \t!?.," ) << '\n';
}
The program output is
10
you can do it easily with regex
int numWords(std::string str)
{
std::regex re("\\S+"); // or `[^ \t\n]+` to exactly match the question
return std::distance(
std::sregex_iterator(str.begin(), str.end(), re),
std::sregex_iterator()
);
}
I'm quite new to c++. My problem is that I have a string that can be any length and ends with \n. For example:
const string s = "Daniel,20;Michael,99\n"
(It's always "name,age;name,age;name,age.............\n")
and I want to separate name and age and put it into two vectors so it can be stored. But I dont know how to manage string with more separators. So the example would be separated like this:
Vector name contains {Daniel,Michael}
Vector age contains {20,99}
You can use stringstream and getline for this purpose, but since you have a very specific format, simple std::string::find is likely to fix your issue. Here is a simple example:
#include <vector>
#include <string>
#include <cstdio>
#include <cstdlib>
#include <cstddef>
int main() {
std::string const s = "Daniel,20;Michael,99;Terry,42;Jack,34";
std::vector<std::string> names;
std::vector<int> ages;
std::size_t beg = 0;
std::size_t end = 0;
while ((end = s.find(',', end)) != s.npos) {
names.emplace_back(s, beg, end - beg);
char* pend;
ages.push_back(std::strtol(s.c_str() + end + 1, &pend, 10));
end = beg = pend - s.c_str() + 1;
}
for (auto&& n : names) std::puts(n.c_str());
for (auto&& a : ages) std::printf("%d\n", a);
}
Sorry my C++ skills have faded, but this is what I would do :-
vector <string> names;
vector <string> ages;
string inputString = "Daniel,20;Michael,99;Terry,42;Jack,34";
string word = "";
for(int i = 0; i<inputString.length(); i++)
{
if(inputString[i] == ';')
{
ages.push_back(word);
word = "";
}
else if (inputString[i] == ',')
{
names.push_back(word);
word = "";
}
else
{
word = word + inputString[i];
}
}
ages.push_back(word);
I have a string of items (see code). I want to say when a specific item from that list is found. In my example I want the output to be 3 since the item is found after the first two items. I can print out the separate items to the console but I cannot figure out how to do a count on these two items. I think it is because of the while loop... I always get numbers like 11 instead of two separate 1s. Any tips? :)
#include <iostream>
#include <string>
using namespace std;
int main() {
string items = "box,cat,dog,cat";
string delim = ",";
size_t pos = 0;
string token;
string item1 = "dog";
int count = 0;
`;
while ((pos = items.find(delim)) != string::npos)
{
token = items.substr(0, pos);
if (token != item1)
{
cout << token << endl; //here I would like to increment count for every
//item before item1 (dog) is found
items.erase(0, pos + 1);
}
else if (token == item1)
return 0;
}
return 0; //output: box cat
}
I replaced your search algorithm with the method explode, that separates your string by a delimiter and returns a vector, which is better suited for searching and getting the element count:
#include <string>
#include <vector>
#include <sstream>
#include <iostream>
#include <algorithm>
std::vector<std::string> explode(const std::string& s, char delim)
{
std::vector<std::string> result;
std::istringstream iss(s);
for (std::string token; std::getline(iss, token, delim); )
{
result.push_back(std::move(token));
}
return result;
}
int main()
{
std::string items = "box,cat,dog,cat";
std::string item1 = "dog";
char delim = ',';
auto resultVec = explode(items, delim);
auto itResult = std::find_if(resultVec.begin(), resultVec.end()
, [&item1](const auto& resultString)
{
return item1 == resultString;
});
if (itResult != resultVec.end())
{
auto index(std::distance(resultVec.begin(), itResult) + 1); // index is zero based
std::cout << index;
}
return 0;
}
By using std::find_if you can get the position of item1 by iterator, which you can use with std::distance to get the count of elements that are in front of it.
Credits for the explode method go to this post: Is there an equivalent in C++ of PHP's explode() function?
There are many ways to Rome. Here an additional solution using a std::regex.
But main approach is the same as the accepted answer. Using modern C++17 language elements, it is a little bit more compact.
#include <iostream>
#include <string>
#include <regex>
#include <iterator>
#include <vector>
const std::regex re{ "," };
int main() {
std::string items{ "box,cat,dog,cat" };
// Split String and put all sub-items in a vector
std::vector subItems(std::sregex_token_iterator(items.begin(), items.end(), re, -1), {});
// Search and check if found and show result
if (auto it = std::find(subItems.begin(), subItems.end(), "dog"); it != subItems.end())
std::cout << "Found at position: " << std::distance(subItems.begin(), it) + 1 << '\n';
else
std::cout << "Not found.\n";
return 0;
}
The function takes a string containing of comma(,) separated numbers as string and converts into numbers. Sometimes it produces a garbage value at the end.
vector<int> parseInts(string str)
{
int as[200]={0};
int i=0,j=0;
for(;str[i]!='\0';i++)
{
while(str[i]!=','&&str[i]!='\0')
{as[j]= as[j]*10 +str[i] -'0';
i++;}
j++;
}
vector<int>rr;
for(int i=0;i<j;i++)
rr.push_back(as[i]);
return rr;
}
If you're writing in C++, use C++ features instead of C-style string manipulation. You can combine std::istringstream, std::getline(), and std::stoi() into a very short solution. (Also note that you should take the argument by const reference since you do not modify it.)
#include <iostream>
#include <sstream>
#include <string>
#include <vector>
std::vector<int> parseInts(std::string const & str) {
std::vector<int> values;
std::istringstream src{str};
std::string buf;
while (std::getline(src, buf, ',')) {
// Note no error checking on this conversion -- exercise for the reader.
values.push_back(std::stoi(buf));
}
return values;
}
(Demo)
The code doesn't handle whitespace and inputs with more than 200 numbers.
An alternative working solution:
#include <iostream>
#include <sstream>
#include <iterator>
#include <algorithm>
#include <vector>
std::vector<int> parseInts(std::string s) {
std::replace(s.begin(), s.end(), ',', ' ');
std::istringstream ss(std::move(s));
return std::vector<int>{
std::istream_iterator<int>{ss},
std::istream_iterator<int>{}
};
}
int main() {
auto v = parseInts("1,2 , 3 ,,, 4,5,,,");
for(auto i : v)
std::cout << i << '\n';
}
Output:
1
2
3
4
5
You never really asked a question. If you are looking for an elegant method, then I provide that below. If you are asking us to debug the code, then that is a different matter.
First here is a nice utility for splitting a string
std::vector<std::string> split(const std::string& str, char delim) {
std::vector<std::string> strings;
size_t start;
size_t end = 0;
while ((start = str.find_first_not_of(delim, end)) != std::string::npos) {
end = str.find(delim, start);
strings.push_back(str.substr(start, end - start));
}
return strings;
}
First split the string on commas:
std::vector<std::string> strings = split(str, ',');
Then covert each to an int
std::vector<int> ints;
for (auto s : strings)
ints.push_back(std::stoi(s))
This question already has answers here:
How do I iterate over the words of a string?
(84 answers)
Closed 4 years ago.
If I have a std::string containing a comma-separated list of numbers, what's the simplest way to parse out the numbers and put them in an integer array?
I don't want to generalise this out into parsing anything else. Just a simple string of comma separated integer numbers such as "1,1,1,1,2,1,1,1,0".
Input one number at a time, and check whether the following character is ,. If so, discard it.
#include <vector>
#include <string>
#include <sstream>
#include <iostream>
int main()
{
std::string str = "1,2,3,4,5,6";
std::vector<int> vect;
std::stringstream ss(str);
for (int i; ss >> i;) {
vect.push_back(i);
if (ss.peek() == ',')
ss.ignore();
}
for (std::size_t i = 0; i < vect.size(); i++)
std::cout << vect[i] << std::endl;
}
Something less verbose, std and takes anything separated by a comma.
stringstream ss( "1,1,1,1, or something else ,1,1,1,0" );
vector<string> result;
while( ss.good() )
{
string substr;
getline( ss, substr, ',' );
result.push_back( substr );
}
Yet another, rather different, approach: use a special locale that treats commas as white space:
#include <locale>
#include <vector>
struct csv_reader: std::ctype<char> {
csv_reader(): std::ctype<char>(get_table()) {}
static std::ctype_base::mask const* get_table() {
static std::vector<std::ctype_base::mask> rc(table_size, std::ctype_base::mask());
rc[','] = std::ctype_base::space;
rc['\n'] = std::ctype_base::space;
rc[' '] = std::ctype_base::space;
return &rc[0];
}
};
To use this, you imbue() a stream with a locale that includes this facet. Once you've done that, you can read numbers as if the commas weren't there at all. Just for example, we'll read comma-delimited numbers from input, and write then out one-per line on standard output:
#include <algorithm>
#include <iterator>
#include <iostream>
int main() {
std::cin.imbue(std::locale(std::locale(), new csv_reader()));
std::copy(std::istream_iterator<int>(std::cin),
std::istream_iterator<int>(),
std::ostream_iterator<int>(std::cout, "\n"));
return 0;
}
The C++ String Toolkit Library (Strtk) has the following solution to your problem:
#include <string>
#include <deque>
#include <vector>
#include "strtk.hpp"
int main()
{
std::string int_string = "1,2,3,4,5,6,7,8,9,10,11,12,13,14,15";
std::vector<int> int_list;
strtk::parse(int_string,",",int_list);
std::string double_string = "123.456|789.012|345.678|901.234|567.890";
std::deque<double> double_list;
strtk::parse(double_string,"|",double_list);
return 0;
}
More examples can be found Here
Alternative solution using generic algorithms and Boost.Tokenizer:
struct ToInt
{
int operator()(string const &str) { return atoi(str.c_str()); }
};
string values = "1,2,3,4,5,9,8,7,6";
vector<int> ints;
tokenizer<> tok(values);
transform(tok.begin(), tok.end(), back_inserter(ints), ToInt());
Lots of pretty terrible answers here so I'll add mine (including test program):
#include <string>
#include <iostream>
#include <cstddef>
template<typename StringFunction>
void splitString(const std::string &str, char delimiter, StringFunction f) {
std::size_t from = 0;
for (std::size_t i = 0; i < str.size(); ++i) {
if (str[i] == delimiter) {
f(str, from, i);
from = i + 1;
}
}
if (from <= str.size())
f(str, from, str.size());
}
int main(int argc, char* argv[]) {
if (argc != 2)
return 1;
splitString(argv[1], ',', [](const std::string &s, std::size_t from, std::size_t to) {
std::cout << "`" << s.substr(from, to - from) << "`\n";
});
return 0;
}
Nice properties:
No dependencies (e.g. boost)
Not an insane one-liner
Easy to understand (I hope)
Handles spaces perfectly fine
Doesn't allocate splits if you don't want to, e.g. you can process them with a lambda as shown.
Doesn't add characters one at a time - should be fast.
If using C++17 you could change it to use a std::stringview and then it won't do any allocations and should be extremely fast.
Some design choices you may wish to change:
Empty entries are not ignored.
An empty string will call f() once.
Example inputs and outputs:
"" -> {""}
"," -> {"", ""}
"1," -> {"1", ""}
"1" -> {"1"}
" " -> {" "}
"1, 2," -> {"1", " 2", ""}
" ,, " -> {" ", "", " "}
You could also use the following function.
void tokenize(const string& str, vector<string>& tokens, const string& delimiters = ",")
{
// Skip delimiters at beginning.
string::size_type lastPos = str.find_first_not_of(delimiters, 0);
// Find first non-delimiter.
string::size_type pos = str.find_first_of(delimiters, lastPos);
while (string::npos != pos || string::npos != lastPos) {
// Found a token, add it to the vector.
tokens.push_back(str.substr(lastPos, pos - lastPos));
// Skip delimiters.
lastPos = str.find_first_not_of(delimiters, pos);
// Find next non-delimiter.
pos = str.find_first_of(delimiters, lastPos);
}
}
std::string input="1,1,1,1,2,1,1,1,0";
std::vector<long> output;
for(std::string::size_type p0=0,p1=input.find(',');
p1!=std::string::npos || p0!=std::string::npos;
(p0=(p1==std::string::npos)?p1:++p1),p1=input.find(',',p0) )
output.push_back( strtol(input.c_str()+p0,NULL,0) );
It would be a good idea to check for conversion errors in strtol(), of course. Maybe the code may benefit from some other error checks as well.
I'm surprised no one has proposed a solution using std::regex yet:
#include <string>
#include <algorithm>
#include <vector>
#include <regex>
void parse_csint( const std::string& str, std::vector<int>& result ) {
typedef std::regex_iterator<std::string::const_iterator> re_iterator;
typedef re_iterator::value_type re_iterated;
std::regex re("(\\d+)");
re_iterator rit( str.begin(), str.end(), re );
re_iterator rend;
std::transform( rit, rend, std::back_inserter(result),
[]( const re_iterated& it ){ return std::stoi(it[1]); } );
}
This function inserts all integers at the back of the input vector. You can tweak the regular expression to include negative integers, or floating point numbers, etc.
#include <sstream>
#include <vector>
const char *input = "1,1,1,1,2,1,1,1,0";
int main() {
std::stringstream ss(input);
std::vector<int> output;
int i;
while (ss >> i) {
output.push_back(i);
ss.ignore(1);
}
}
Bad input (for instance consecutive separators) will mess this up, but you did say simple.
string exp = "token1 token2 token3";
char delimiter = ' ';
vector<string> str;
string acc = "";
for(int i = 0; i < exp.size(); i++)
{
if(exp[i] == delimiter)
{
str.push_back(acc);
acc = "";
}
else
acc += exp[i];
}
bool GetList (const std::string& src, std::vector<int>& res)
{
using boost::lexical_cast;
using boost::bad_lexical_cast;
bool success = true;
typedef boost::tokenizer<boost::char_separator<char> > tokenizer;
boost::char_separator<char> sepa(",");
tokenizer tokens(src, sepa);
for (tokenizer::iterator tok_iter = tokens.begin();
tok_iter != tokens.end(); ++tok_iter) {
try {
res.push_back(lexical_cast<int>(*tok_iter));
}
catch (bad_lexical_cast &) {
success = false;
}
}
return success;
}
I cannot yet comment (getting started on the site) but added a more generic version of Jerry Coffin's fantastic ctype's derived class to his post.
Thanks Jerry for the super idea.
(Because it must be peer-reviewed, adding it here too temporarily)
struct SeparatorReader: std::ctype<char>
{
template<typename T>
SeparatorReader(const T &seps): std::ctype<char>(get_table(seps), true) {}
template<typename T>
std::ctype_base::mask const *get_table(const T &seps) {
auto &&rc = new std::ctype_base::mask[std::ctype<char>::table_size]();
for(auto &&sep: seps)
rc[static_cast<unsigned char>(sep)] = std::ctype_base::space;
return &rc[0];
}
};
This is the simplest way, which I used a lot. It works for any one-character delimiter.
#include<bits/stdc++.h>
using namespace std;
int main() {
string str;
cin >> str;
int temp;
vector<int> result;
char ch;
stringstream ss(str);
do
{
ss>>temp;
result.push_back(temp);
}while(ss>>ch);
for(int i=0 ; i < result.size() ; i++)
cout<<result[i]<<endl;
return 0;
}
simple structure, easily adaptable, easy maintenance.
std::string stringIn = "my,csv,,is 10233478,separated,by commas";
std::vector<std::string> commaSeparated(1);
int commaCounter = 0;
for (int i=0; i<stringIn.size(); i++) {
if (stringIn[i] == ",") {
commaSeparated.push_back("");
commaCounter++;
} else {
commaSeparated.at(commaCounter) += stringIn[i];
}
}
in the end you will have a vector of strings with every element in the sentence separated by spaces. empty strings are saved as separate items.
Simple Copy/Paste function, based on the boost tokenizer.
void strToIntArray(std::string string, int* array, int array_len) {
boost::tokenizer<> tok(string);
int i = 0;
for(boost::tokenizer<>::iterator beg=tok.begin(); beg!=tok.end();++beg){
if(i < array_len)
array[i] = atoi(beg->c_str());
i++;
}
void ExplodeString( const std::string& string, const char separator, std::list<int>& result ) {
if( string.size() ) {
std::string::const_iterator last = string.begin();
for( std::string::const_iterator i=string.begin(); i!=string.end(); ++i ) {
if( *i == separator ) {
const std::string str(last,i);
int id = atoi(str.c_str());
result.push_back(id);
last = i;
++ last;
}
}
if( last != string.end() ) result.push_back( atoi(&*last) );
}
}
#include <sstream>
#include <vector>
#include <algorithm>
#include <iterator>
const char *input = ",,29870,1,abc,2,1,1,1,0";
int main()
{
std::stringstream ss(input);
std::vector<int> output;
int i;
while ( !ss.eof() )
{
int c = ss.peek() ;
if ( c < '0' || c > '9' )
{
ss.ignore(1);
continue;
}
if (ss >> i)
{
output.push_back(i);
}
}
std::copy(output.begin(), output.end(), std::ostream_iterator<int> (std::cout, " ") );
return 0;
}