Count character occurrences in a string in C++ - c++

Question

How can I count the number of "_" in a string like "bla_bla_blabla_bla"?

Answer 1

#include <algorithm>
std::string s = "a_b_c";
std::string::difference_type n = std::count(s.begin(), s.end(), '_');

Answer 2

Pseudocode:
count = 0
For each character c in string s
Check if c equals '_'
If yes, increase count
EDIT: C++ example code:
int count_underscores(string s) {
int count = 0;
for (int i = 0; i < s.size(); i++)
if (s[i] == '_') count++;
return count;
}
Note that this is code to use together with std::string, if you're using char*, replace s.size() with strlen(s).
Also note: I can understand you want something "as small as possible", but I'd suggest you to use this solution instead. As you see you can use a function to encapsulate the code for you so you won't have to write out the for loop everytime, but can just use count_underscores("my_string_") in the rest of your code. Using advanced C++ algorithms is certainly possible here, but I think it's overkill.

Answer 3

Old-fashioned solution with appropriately named variables. This gives the code some spirit.
#include <cstdio>
int _(char*__){int ___=0;while(*__)___='_'==*__++?___+1:___;return ___;}int main(){char*__="_la_blba_bla__bla___";printf("The string \"%s\" contains %d _ characters\n",__,_(__));}
Edit: about 8 years later, looking at this answer I'm ashamed I did this (even though I justified it to myself as a snarky poke at a low-effort question). This is toxic and not OK. I'm not removing the post; I'm adding this apology to help shifting the atmosphere on StackOverflow. So OP: I apologize and I hope you got your homework right despite my trolling and that answers like mine did not discourage you from participating on the site.

Answer 4

Using the lambda function to check the character is "_" then the only count will be incremented else not a valid character
std::string s = "a_b_c";
size_t count = std::count_if( s.begin(), s.end(), []( char c ){return c =='_';});
std::cout << "The count of numbers: " << count << std::endl;

Answer 5

#include <boost/range/algorithm/count.hpp>
std::string str = "a_b_c";
int cnt = boost::count(str, '_');

Answer 6

You name it... Lambda version... :)
using namespace boost::lambda;
std::string s = "a_b_c";
std::cout << std::count_if (s.begin(), s.end(), _1 == '_') << std::endl;
You need several includes... I leave you that as an exercise...

Answer 7

Count character occurrences in a string is easy:
#include <bits/stdc++.h>
using namespace std;
int main()
{
string s="Sakib Hossain";
int cou=count(s.begin(),s.end(),'a');
cout<<cou;
}

Answer 8

There are several methods of std::string for searching, but find is probably what you're looking for. If you mean a C-style string, then the equivalent is strchr. However, in either case, you can also use a for loop and check each character—the loop is essentially what these two wrap up.
Once you know how to find the next character given a starting position, you continually advance your search (i.e. use a loop), counting as you go.

Answer 9

I would have done it this way :
#include <iostream>
#include <string>
using namespace std;
int main()
{
int count = 0;
string s("Hello_world");
for (int i = 0; i < s.size(); i++)
{
if (s.at(i) == '_')
count++;
}
cout << endl << count;
cin.ignore();
return 0;
}

Answer 10

You can find out occurrence of '_' in source string by using string functions.
find() function takes 2 arguments , first - string whose occurrences we want to find out and second argument takes starting position.While loop is use to find out occurrence till the end of source string.
example:
string str2 = "_";
string strData = "bla_bla_blabla_bla_";
size_t pos = 0,pos2;
while ((pos = strData.find(str2, pos)) < strData.length())
{
printf("\n%d", pos);
pos += str2.length();
}

Answer 11

The range based for loop comes in handy
int countUnderScores(string str)
{
int count = 0;
for (char c: str)
if (c == '_') count++;
return count;
}
int main()
{
string str = "bla_bla_blabla_bla";
int count = countUnderScores(str);
cout << count << endl;
}

Answer 12

I would have done something like that :)
const char* str = "bla_bla_blabla_bla";
char* p = str;
unsigned int count = 0;
while (*p != '\0')
if (*p++ == '_')
count++;

Answer 13

Try
#include <iostream>
#include <string>
using namespace std;
int WordOccurrenceCount( std::string const & str, std::string const & word )
{
int count(0);
std::string::size_type word_pos( 0 );
while ( word_pos!=std::string::npos )
{
word_pos = str.find(word, word_pos );
if ( word_pos != std::string::npos )
{
++count;
// start next search after this word
word_pos += word.length();
}
}
return count;
}
int main()
{
string sting1="theeee peeeearl is in theeee riveeeer";
string word1="e";
cout<<word1<<" occurs "<<WordOccurrenceCount(sting1,word1)<<" times in ["<<sting1 <<"] \n\n";
return 0;
}

Answer 14

public static void main(String[] args) {
char[] array = "aabsbdcbdgratsbdbcfdgs".toCharArray();
char[][] countArr = new char[array.length][2];
int lastIndex = 0;
for (char c : array) {
int foundIndex = -1;
for (int i = 0; i < lastIndex; i++) {
if (countArr[i][0] == c) {
foundIndex = i;
break;
}
}
if (foundIndex >= 0) {
int a = countArr[foundIndex][1];
countArr[foundIndex][1] = (char) ++a;
} else {
countArr[lastIndex][0] = c;
countArr[lastIndex][1] = '1';
lastIndex++;
}
}
for (int i = 0; i < lastIndex; i++) {
System.out.println(countArr[i][0] + " " + countArr[i][1]);
}
}