string Search Operations

The string class provides six search functions, each named as a variant of find . The operations all return a string::size_type value that is the index of where the match occurred,  or a special value named string::npos if there is no match. The string class defines npos as a value that is guaranteed to be greater than any valid index.

 

There are four versions of each of the search operations, each of which takes a different set of arguments . The arguments to the search operations are listed below. Basically, these operations differ as to whether they are looking for a single character , another string , a C-style null-terminated string , or a given number of characters from a character array .

 

string Search Operations
s.find(args)	Find first occurrence of args in s.
s.rfind(args)	Find last occurrence of args in s.
s.find_first_of(args)	Find first occurrence of any character from args in s.
s.find_last_of(args)	Find last occurrence of any character from args in s.
s.find_first_not_of(args)	Find first character in s that is not in args.
s.find_last_not_of(args)	Find last character in s that is not in args.
Arguments to string find Operations
c, pos	Look for the character c starting at position pos in s.pos defaults to 0 .
s2, pos	Look for the string s2 starting at position pos in s.pos default to 0 .
cp, pos	Look for the C-style null-terminated string pointed to by the pointer cp. Start looking starting at position pos in s.pos defaults to 0 .
cp, pos, n	Look for the first n characters in the array pointed to by the pointer cp. Start looking starting at position pos in s. No default for pos or n.

/* To calcualte the sentence has many words, and then print the longest words and shortest words if has. 2010-4-1 wcdj (April Fool's Day) */ #include <iostream> #include <vector> #include <string> using namespace std; int main() { string line1="We were her pride of 10 she named us:"; string line2="Benjamin, Phoenix, the Prodigal"; string line3="and perspicacious pacific Suzanne"; string sentence=line1+' '+line2+' '+line3; string word; string::size_type maxLen, minLen, wordLen, count=0; vector<string> longestWords, shortestWords; string::size_type startPos=0, endPos=0; string separators(" :,"); while ((startPos=sentence.find_first_not_of(separators,endPos))!=string::npos) { ++count; endPos=sentence.find_first_of(separators,startPos); if (endPos==string::npos) { wordLen=sentence.size()-startPos; } else { wordLen=endPos-startPos; } word.assign(sentence.begin()+startPos, sentence.begin()+startPos+wordLen);// get word if (count==1)// the first word { maxLen=minLen=wordLen; longestWords.push_back(word); shortestWords.push_back(word); } else { if (wordLen>maxLen) { maxLen=wordLen; longestWords.clear();// clear former data longestWords.push_back(word); } else if (wordLen==maxLen)// same as the current longestWord { longestWords.push_back(word); } if (wordLen<minLen) { minLen=wordLen; shortestWords.clear();// clear former data shortestWords.push_back(word); } else if (wordLen==minLen)// same as the current shortestWord { shortestWords.push_back(word); } } } // print the number of words cout<<"word amount: "<<count<<endl; vector<string>::iterator iter; // print the longest words cout<<"longest word(s): "<<endl; for (iter=longestWords.begin(); iter!=longestWords.end(); ++iter) { cout<<*iter<<endl; } // print the shortest words cout<<"shortest word(s): "<<endl; for (iter=shortestWords.begin(); iter!=shortestWords.end(); ++iter) { cout<<*iter<<endl; } return 0; } /* output: word amount: 17 longest word(s): perspicacious shortest word(s): We of 10 us Press any key to continue */