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Trying to use find_if function to locate value in vector of pairs by first element


Trying to use find_if function to locate value in vector of pairs by first element

By : habourret
Date : October 23 2020, 06:10 AM
wish helps you The problem is there is no built-in comparison between a pair and what appears to be a string. You will have to provide one. Eg.
code :
it = find_if (vect.begin(), 
              vect.end(), 
              [currentword](const pair <string,int>& p){ // this is a lambda expression
                  return p.first == currentword; // compare strings
              });
std::map<string, int> freqmap;
freqmap[currentword]++;


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Find_if function in vector

Find_if function in vector


By : Abubaker Sarang
Date : March 29 2020, 07:55 AM
Any of those help Find_if is an function of an and returns an iterator to the first element in the range.
code :
   #include <list>
  #include <algorithm>
  #include <iostream>

  bool greater10 ( int value )
  {
  if(value == 10)
   {
    return true;
   }
   return false;
  }

 int main( )
  {
       using namespace std;

       list <int> L;
       list <int>::iterator Iter;
      list <int>::iterator result;

      L.push_back( 10 );
      L.push_back( 9 );
      L.push_back( 15 );
      L.push_back( 8);
      L.push_back( 10 );

     cout << "L = ( " ;
      for ( Iter = L.begin( ) ; Iter != L.end( ) ; Iter++ )
          cout << *Iter << " ";
      cout << ")" << endl;


      result = find_if( L.begin( ), L.end( ), &greater10 );
      for( ;result != L.end(); result++ )
       {
      cout << *result <<"\t";
         cout <<endl;
      }
  }
std::find_if for custom objects returns bad iterator when vector has at least 1 element

std::find_if for custom objects returns bad iterator when vector has at least 1 element


By : user3254095
Date : March 29 2020, 07:55 AM
this one helps. The code you wrote isn't portable because it uses implementation-specific _Ptr member of vector::iterator, and therefore there are no requirements on that member to be nullptr. Change
code :
if (player._Ptr != nullptr)
if (player != m_playerList.end())
Access an element in a vector of pairs by a key besides find_if() or iterators

Access an element in a vector of pairs by a key besides find_if() or iterators


By : user1179004
Date : March 29 2020, 07:55 AM
Hope this helps
I'm trying to access an element by using the keys like an index. Unfortunately, I always receive a segmentation fault.
code :
MyWords[key1].second[key2].second.count[0] = A_Number_Here;
#include <iostream>
#include <vector>
#include <algorithm>

struct Item
{
   std::string word;
   std::vector<int> count; // changed to vector array
};
using Pair = std::pair<int, std::vector< std::pair<int, Item> > >;

int main()
{
   std::vector< Pair > MyWords =
   {  //int, <std::pair<int,          Item            > > >
      {1   , {        {    4,  Item{"String1", {1,2,3}} } }       },
      {0   , {        {    5,  Item{"String2", {5,2,8}} } }       },
      {2   , {        {    8,  Item{"String3", {1,7,9}} }, {    9,  Item{"String4", {11,77,99}} } }       }
   };

   for(const auto& bigPair: MyWords)
   {
      std::cout << "Key : " << bigPair.first;

      for(const auto& smallPair: bigPair.second)
      {
         std::cout << "\nValues: " << smallPair.first << "\t";

         std::cout << smallPair.second.word << " "
                  << smallPair.second.count[0] << " "
                  << smallPair.second.count[1] << " "
                  << smallPair.second.count[2] ;
      }
      std::cout << "\n\n";
   }

   return 0;
}
Using std::find_if with std::vector to find smallest element greater than some value

Using std::find_if with std::vector to find smallest element greater than some value


By : Scott
Date : March 29 2020, 07:55 AM
it fixes the issue 1 line of code is necessary, if a lambda function is used: x is a local double (value we are searching for) const double x = 5.5
code :
std::find_if(vec.cbegin(), vec.cend(), [x] (double element) { return (x < element); })
std::find_if(vec.cbegin(), vec.cend(), lambda)
[x] (double element) { return (x < element); }
Find int in Vector of pairs vector <pair <int, vector <SavingsAccount*>>> using find_if

Find int in Vector of pairs vector <pair <int, vector <SavingsAccount*>>> using find_if


By : Omer Alhalabi
Date : March 29 2020, 07:55 AM
fixed the issue. Will look into that further My data structure is: , Use a lambda as predicate for std::find_if():
code :
#include <algorithm>
#include <utility>
#include <vector>
#include <iostream>

using namespace std;

struct SavingsAccount{};

int main()
{
    vector<pair<int, vector<SavingsAccount>>> accVec;
    vector<pair<int, vector<SavingsAccount>>>::iterator iter;

    do {
        cout << "Enter The Account Number In Which You Want To Deposit: ";
        int accID;
        cin >> accID;

        iter = find_if(accVec.begin(), accVec.end(),
                       [=](pair<int, vector<SavingsAccount>> const &accPair) {
                           return accPair.first == accID;
                       }
        );

        if (iter == accVec.end()) {
            cout << endl << "ERROR: Account Does Not Exist. Try Again." << endl;
        }
    } while (iter == accVec.end());
}
#include <algorithm>
#include <utility>
#include <vector>
#include <iostream>

using namespace std;

struct SavingsAccount{};

class AccountFinder
{
    int accID;

public:
    AccountFinder(int accID) : accID{ accID } {};

    bool operator()(pair<int, vector<SavingsAccount>> const &accPair)
    {
        return accPair.first == accID;
    }
};

int main()
{
    vector<pair<int, vector<SavingsAccount>>> accVec;
    vector<pair<int, vector<SavingsAccount>>>::iterator iter;

    do {
        cout << "Enter The Account Number In Which You Want To Deposit: ";
        int accID;
        cin >> accID;

        iter = find_if(accVec.begin(), accVec.end(), AccountFinder(accID));

        if (iter == accVec.end()) {
            cout << endl << "ERROR: Account Does Not Exist. Try Again." << endl;
        }
    } while (iter == accVec.end());
}
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