CppGetLongestStringLength.md

 

 

 

 

 

(C++) GetLongestStringLength

 

GetLongestStringLength is a std::string and container code snippet to obtain the length/size of the longest/largest std::string in a container.

 

There are multiple versions of GetLongestStringLength:

 

• GetLongestStringLength using C++98 and a for-loop
• GetLongestStringLength using C++98 and a global functor
• GetLongestStringLength using boost::bind and boost::lambda
• GetLongestStringLength using BOOST_FOREACH
• GetLongestStringLength using C++11

 

 

 

 

 

GetLongestStringLength using C++98 and a for-loop

 

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#include <string> #include <vector> int GetLongestStringLength(const std::vector<std::string>& v) {   int longest = 0;   const int sz = v.size();   for (int i=0; i!=sz; ++i)   {     longest = std::max(static_cast<int>(v[i].size()),longest);   }   return longest; }

 

 

 

 

 

GetLongestStringLength using C++98 and a global functor

 

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#include <algorithm> #include <string> #include <vector> bool StringLengthCompare(const std::string& lhs, const std::string& rhs) {   return lhs.size() < rhs.size(); } int GetLongestStringLength(const std::vector<std::string>& v) {   const std::vector<std::string>::const_iterator i     = std::max_element(       v.begin(),       v.end(),       StringLengthCompare     );   if (i!=v.end()) return static_cast<int>(i->size());   return 0; }

 

 

 

 

 

GetLongestStringLength using boost::bind and boost::lambda

 

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#include <algorithm> #include <string> #include <vector> #include <boost/bind.hpp> #include <boost/lambda/lambda.hpp> int GetLongestStringLength(const std::vector<std::string>& v) {   const std::vector<std::string>::const_iterator i     = std::max_element(       v.begin(),       v.end(),       boost::bind(&std::string::size,boost::lambda::_1) < boost::bind(&std::string::size,boost::lambda::_2)     );   if (i!=v.end()) return static_cast<int>(i->size());   return 0; }

 

 

 

 

 

GetLongestStringLength using BOOST_FOREACH

 

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#include <string> #include <vector> #include <boost/foreach.hpp> int GetLongestStringLength(const std::vector<std::string>& v) {   int longest = 0;   BOOST_FOREACH(const std::string& s,v)   {     longest = std::max(static_cast<int>(s.size()),longest);   }   return longest; }

 

 

 

 

 

GetLongestStringLength using C++11

 

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#include <algorithm> #include <string> #include <vector> int GetLongestStringLength(const std::vector<std::string>& v) {   const std::vector<std::string>::const_iterator i     = std::max_element(       v.begin(),       v.end(),       [](const std::string& lhs, const std::string& rhs)       {         return lhs.size() < rhs.size();       }     );   if (i!=v.end()) return static_cast<int>(i->size());   return 0; }

 

 

 

 

 

Testing code

 

• Download the Qt Creator project 'CppGetLongestStringLength' (zip)

 

 

 

 

 

Technical facts

 

Application type(s)

• Desktop application

Operating system(s) or programming environment(s)

• Lubuntu 12.10 (quantal)

IDE(s):

• Qt Creator 2.5.2

Project type:

• Console application

C++ standard:

• C++11

Compiler(s):

• G++ 4.7.2

Libraries used:

• STL: GNU ISO C++ Library, version 4.7.2

 

 

 

 

 

Qt project file: CppGetLongestStringLength.pro

 

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TEMPLATE = app CONFIG += console CONFIG -= qt SOURCES += main.cpp QMAKE_CXXFLAGS += -std=c++11 -Wall -Wextra -Weffc++ -Werror

 

 

 

 

 

main.cpp

 

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#include <algorithm> #include <string> #include <vector> int GetLongestStringLengthCpp11(const std::vector<std::string>& v) {   const std::vector<std::string>::const_iterator i     = std::max_element(       v.begin(),       v.end(),       [](const std::string& lhs, const std::string& rhs)       {         return lhs.size() < rhs.size();       }     );   if (i!=v.end()) return static_cast<int>(i->size());   return 0; } int GetLongestStringLengthCpp98ForLoop(const std::vector<std::string>& v) {   int longest = 0;   const int sz = v.size();   for (int i=0; i!=sz; ++i)   {     longest = std::max(static_cast<int>(v[i].size()),longest);   }   return longest; } #ifdef IF_I_ONLY_KNEW_HOW_TO_GET_THIS_WORKING_7737346578649782927896 #include <functional> int GetLongestStringLengthCpp98Functor(const std::vector<std::string>& v) {   const std::vector<std::string>::const_iterator i     = std::max_element(       v.begin(),       v.end(),       std::mem_fun_ref(&std::string::size)     );   if (i!=v.end()) return static_cast<int>(i->size());   return 0; } #endif bool StringLengthCompare(const std::string& lhs, const std::string& rhs) {   return lhs.size() < rhs.size(); } int GetLongestStringLengthCpp98CustomFunctor(const std::vector<std::string>& v) {   const std::vector<std::string>::const_iterator i     = std::max_element(       v.begin(),       v.end(),       StringLengthCompare     );   if (i!=v.end()) return static_cast<int>(i->size());   return 0; } #include <boost/foreach.hpp> int GetLongestStringLengthBoostForeach(const std::vector<std::string>& v) {   int longest = 0;   BOOST_FOREACH(const std::string& s,v)   {     longest = std::max(static_cast<int>(s.size()),longest);   }   return longest; } #include <boost/bind.hpp> #include <boost/lambda/lambda.hpp> int GetLongestStringLengthBoostBind(const std::vector<std::string>& v) {   const std::vector<std::string>::const_iterator i     = std::max_element(       v.begin(),       v.end(),       boost::bind(&std::string::size,boost::lambda::_1) < boost::bind(&std::string::size,boost::lambda::_2)     );   if (i!=v.end()) return static_cast<int>(i->size());   return 0; } #include <cassert> int main() {   {     const std::vector<std::string> v = { "1","123","123456","12345678","123456789" };     const int expected = 9;     assert(GetLongestStringLengthCpp11(v) == expected);     assert(GetLongestStringLengthBoostBind(v) == expected);     assert(GetLongestStringLengthBoostForeach(v) == expected);     assert(GetLongestStringLengthCpp98CustomFunctor(v) == expected);     assert(GetLongestStringLengthCpp98ForLoop(v) == expected);   }   {     const std::vector<std::string> v = { "1","23","456","78","123456789","01","23","456","78","9" };     const int expected = 9;     assert(GetLongestStringLengthCpp11(v) == expected);     assert(GetLongestStringLengthBoostBind(v) == expected);     assert(GetLongestStringLengthBoostForeach(v) == expected);     assert(GetLongestStringLengthCpp98CustomFunctor(v) == expected);     assert(GetLongestStringLengthCpp98ForLoop(v) == expected);   }   {     const std::vector<std::string> v = { "x" };     const int expected = 1;     assert(GetLongestStringLengthCpp11(v) == expected);     assert(GetLongestStringLengthBoostBind(v) == expected);     assert(GetLongestStringLengthBoostForeach(v) == expected);     assert(GetLongestStringLengthCpp98CustomFunctor(v) == expected);     assert(GetLongestStringLengthCpp98ForLoop(v) == expected);   }   {     const std::vector<std::string> v = { };     const int expected = 0;     assert(GetLongestStringLengthCpp11(v) == expected);     assert(GetLongestStringLengthBoostBind(v) == expected);     assert(GetLongestStringLengthBoostForeach(v) == expected);     assert(GetLongestStringLengthCpp98CustomFunctor(v) == expected);     assert(GetLongestStringLengthCpp98ForLoop(v) == expected);   } }