blocks|key|1126558|text|#include+<algorithm>

std::string+s+=+"a_b_c";
size_t+n+=+std::count(s.begin(),+s.end(),+'_');|type|code-block|depth|inlineStyleRanges|entityRanges|data|syntax|javascript|1126559|unstyled|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|G|8|@]|9|@]|A|$B|C]]|$1|D|3|-4|5|E|7|H|8|@]|9|@]|A|$]]]|F|$]]

<pre><code>#include &lt;algorithm&gt;

std::string s = "a_b_c";
size_t n = std::count(s.begin(), s.end(), '_');
</code></pre>

blocks|key|1126475|text|伪码：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1126476|count+=+0
For+each+character+c+in+string+s
++Check+if+c+equals+'_'
++++If+yes,+increase+count|code-block|syntax|javascript|1126477|编辑:+C%2B%2B示例代码：|1126478|int+count_underscores(string+s)+{
++int+count+=+0;

++for+(int+i+=+0;+i+<+s.size();+i%2B%2B)
++++if+(s[i]+==+'_')+count%2B%2B;

++return+count;
}|1126479|注意，这是与std::string一起使用的代码，如果您使用的是char*，请将s.size()替换为strlen(s)。|offset|length|style|CODE|1126480|另请注意:我可以理解你想要“尽可能小”的东西，但我建议你改用这个解决方案。如您所见，您可以使用一个函数来封装代码，这样就不必每次都写出for循环，而只需在其余代码中使用count_underscores("my_string_")即可。在这里使用先进的C%2B%2B算法当然是可能的，但我认为这有点过分了。|1126481|entityMap^0|0|0|0|0|6|B|W|5|14|8|1F|9|0|1V|3|2C|V|0^^$0|@$1|2|3|4|5|6|7|U|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|V|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|W|8|@]|9|@]|A|$]]|$1|I|3|J|5|D|7|X|8|@]|9|@]|A|$E|F]]|$1|K|3|L|5|6|7|Y|8|@$M|Z|N|10|O|P]|$M|11|N|12|O|P]|$M|13|N|14|O|P]|$M|15|N|16|O|P]]|9|@]|A|$]]|$1|Q|3|R|5|6|7|17|8|@$M|18|N|19|O|P]|$M|1A|N|1B|O|P]]|9|@]|A|$]]|$1|S|3|-4|5|6|7|1C|8|@]|9|@]|A|$]]]|T|$]]

Pseudocode:

<pre><code>count = 0
For each character c in string s
 Check if c equals '_'
 If yes, increase count
</code></pre>

EDIT: C++ example code:

<pre><code>int count_underscores(string s) {
 int count = 0;

 for (int i = 0; i &lt; s.size(); i++)
 if (s[i] == '_') count++;

 return count;
}
</code></pre>

Note that this is code to use together with <code>std::string</code>, if you're using <code>char*</code>, replace <code>s.size()</code> with <code>strlen(s)</code>.

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 <code>for</code> loop everytime, but can just use <code>count_underscores("my_string_")</code> in the rest of your code. Using advanced C++ algorithms is certainly possible here, but I think it's overkill.

blocks|key|1126593|text|#include+<boost/range/algorithm/count.hpp>

std::string+str+=+"a_b_c";
int+cnt+=+boost::count(str,+'_');|type|code-block|depth|inlineStyleRanges|entityRanges|data|syntax|javascript|1126594|unstyled|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|G|8|@]|9|@]|A|$B|C]]|$1|D|3|-4|5|E|7|H|8|@]|9|@]|A|$]]]|F|$]]

<pre><code>#include &lt;boost/range/algorithm/count.hpp&gt;

std::string str = "a_b_c";
int cnt = boost::count(str, '_');
</code></pre>

blocks|key|1126746|text|使用lambda函数检查字符是否为"_“，则唯一的计数将递增，否则不是有效字符|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1126747|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;|code-block|syntax|javascript|1126748|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

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

blocks|key|1126518|text|你能想到的..。Lambda版本...:)|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1126519|using+namespace+boost::lambda;

std::string+s+=+"a_b_c";
std::cout+<<+std::count_if+(s.begin(),+s.end(),+_1+==+'_')+<<+std::endl;|code-block|syntax|javascript|1126520|您需要几个includes...我把它留给你作为练习...|1126521|entityMap^0|0|0|0^^$0|@$1|2|3|4|5|6|7|K|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|L|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|M|8|@]|9|@]|A|$]]|$1|I|3|-4|5|6|7|N|8|@]|9|@]|A|$]]]|J|$]]

You name it... Lambda version... :)

<pre><code>using namespace boost::lambda;

std::string s = "a_b_c";
std::cout &lt;&lt; std::count_if (s.begin(), s.end(), _1 == '_') &lt;&lt; std::endl;
</code></pre>

You need several includes... I leave you that as an exercise...

blocks|key|911673|text|对字符串中出现的字符进行计数很容易：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|911674|#include+<bits/stdc%2B%2B.h>
using+namespace+std;
int+main()
{
++++string+s="Sakib+Hossain";
++++int+cou=count(s.begin(),s.end(),'a');
++++cout<<cou;
}|code-block|syntax|javascript|911675|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

Count character occurrences in a string is easy:

<pre><code>#include &lt;bits/stdc++.h&gt;
using namespace std;
int main()
{
 string s="Sakib Hossain";
 int cou=count(s.begin(),s.end(),'a');
 cout&lt;&lt;cou;
}
</code></pre>

blocks|key|1126554|text|std::string有几种搜索方法，但find可能就是您要查找的。如果您指的是C样式的字符串，那么等效的字符串就是strchr。但是，在这两种情况下，您也可以使用for循环并检查每个字符-该循环本质上是这两个字符包装。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1126555|一旦你知道了如何找到给定起始位置的下一个字符，你就会不断地前进你的搜索(例如使用循环)，随着你的前进而计数。|1126556|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|F|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|G|8|@]|9|@]|A|$]]|$1|D|3|-4|5|6|7|H|8|@]|9|@]|A|$]]]|E|$]]

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.

blocks|key|911715|text|我会这样做的：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|911716|#include+<iostream>
#include+<string>
using+namespace+std;
int+main()
{

int+count+=+0;
string+s("Hello_world");

for+(int+i+=+0;+i+<+s.size();+i%2B%2B)+
++++{
+++++++if+(s.at(i)+==+'_')++++
+++++++++++count%2B%2B;
++++}
cout+<<+endl+<<+count;
cin.ignore();
return+0;
}|code-block|syntax|javascript|911717|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

I would have done this way : 

<pre><code>#include &lt;iostream&gt;
#include &lt;string&gt;
using namespace std;
int main()
{

int count = 0;
string s("Hello_world");

for (int i = 0; i &lt; s.size(); i++) 
 {
 if (s.at(i) == '_') 
 count++;
 }
cout &lt;&lt; endl &lt;&lt; count;
cin.ignore();
return 0;
}
</code></pre>

blocks|key|911650|text|您可以通过字符串函数找到源字符串中'_‘的出现情况。position.While+()函数有两个参数，第一个参数是我们想要找出的字符串，第二个参数是开始的find循环，用来找出出现的地方，直到源字符串的末尾。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|911651|示例：|911652|string+str2+=+"_";
string+strData+=+"bla_bla_blabla_bla_";

size_t+pos+=+0,pos2;

while+((pos+=+strData.find(str2,+pos))+<+strData.length())+
{
++++printf("\n%25d",+pos);
++++pos+%2B=+str2.length();
}+|code-block|syntax|javascript|911653|entityMap^0|0|0|0^^$0|@$1|2|3|4|5|6|7|K|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|L|8|@]|9|@]|A|$]]|$1|D|3|E|5|F|7|M|8|@]|9|@]|A|$G|H]]|$1|I|3|-4|5|6|7|N|8|@]|9|@]|A|$]]]|J|$]]

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:

<pre><code>string str2 = "_";
string strData = "bla_bla_blabla_bla_";

size_t pos = 0,pos2;

while ((pos = strData.find(str2, pos)) &lt; strData.length()) 
{
 printf("\n%d", pos);
 pos += str2.length();
} 
</code></pre>

blocks|key|1126776|text|我可能会这样做:)|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1126777|const+char*+str+=+"bla_bla_blabla_bla";
char*+p+=+str;++++
unsigned+int+count+=+0;
while+(*p+!=+'\0')
++++if+(*p%2B%2B+==+'_')
++++++++count%2B%2B;|code-block|syntax|javascript|1126778|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

I would have done something like that :)

<pre><code>const char* str = "bla_bla_blabla_bla";
char* p = str; 
unsigned int count = 0;
while (*p != '\0')
 if (*p++ == '_')
 count++;
</code></pre>

blocks|key|1126575|text|试一试|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1126576|#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+)
+++++++++++++++{
+++++++++++++++++++++++%2B%2Bcount;

+++++++++//+start+next+search+after+this+word+
+++++++++++++++++++++++word_pos+%2B=+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;
}|code-block|syntax|javascript|1126577|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

Try

<pre><code>#include &lt;iostream&gt;
 #include &lt;string&gt;
 using namespace std;


int WordOccurrenceCount( std::string const &amp; str, std::string const &amp; 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&lt;&lt;word1&lt;&lt;" occurs "&lt;&lt;WordOccurrenceCount(sting1,word1)&lt;&lt;" times in ["&lt;&lt;sting1 &lt;&lt;"] \n\n";

 return 0;
}
</code></pre>

blocks|key|911683|text|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%2B%2B)+{
++++++++++++++++if+(countArr[i][0]+==+c)+{
++++++++++++++++++++foundIndex+=+i;
++++++++++++++++++++break;
++++++++++++++++}
++++++++++++}
++++++++++++if+(foundIndex+>=+0)+{
++++++++++++++++int+a+=+countArr[foundIndex][1];
++++++++++++++++countArr[foundIndex][1]+=+(char)+%2B%2Ba;
++++++++++++}+else+{
++++++++++++++++countArr[lastIndex][0]+=+c;
++++++++++++++++countArr[lastIndex][1]+=+'1';
++++++++++++++++lastIndex%2B%2B;
++++++++++++}
++++++++}
++++++++for+(int+i+=+0;+i+<+lastIndex;+i%2B%2B)+{
++++++++++++System.out.println(countArr[i][0]+%2B+"+"+%2B+countArr[i][1]);
++++++++}
++++}|type|code-block|depth|inlineStyleRanges|entityRanges|data|syntax|javascript|911684|unstyled|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|G|8|@]|9|@]|A|$B|C]]|$1|D|3|-4|5|E|7|H|8|@]|9|@]|A|$]]]|F|$]]

<pre><code>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 &lt; lastIndex; i++) {
 if (countArr[i][0] == c) {
 foundIndex = i;
 break;
 }
 }
 if (foundIndex &gt;= 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 &lt; lastIndex; i++) {
 System.out.println(countArr[i][0] + " " + countArr[i][1]);
 }
 }
</code></pre>

How can I count the number of <code>"_"</code> in a string like <code>"bla_bla_blabla_bla"</code>?

Count character occurrences in a string in C++

如何计算像"bla_bla_blabla_bla"这样的字符串中的"_"数量

问统计C++中字符串中的字符出现次数
EN

回答 12

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问统计C++中字符串中的字符出现次数EN

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问统计C++中字符串中的字符出现次数
EN