Question

I have following program which crashed at upper bound call. I am not getting why there is a crash. Any reason why I am having a crash. Thanks for your help and time.

#include <iostream>
#include <algorithm>
#include <vector>

using namespace std;

enum quality { good = 0, bad, uncertain };

struct sValue {
   int time;
   int value;
   int qual;
};

struct CompareLowerBoundValueAndTime { 
    bool operator()( const sValue& v, int time ) const {
        return v.time < time;
    } 

    bool operator()( const sValue& v1, const sValue& v2 ) const { 
        return v1.time < v2.time; 
    }

    bool operator()( int time1, int time2 ) const { 
        return time1 < time2; 
    }   

    bool operator()( int time, const sValue& v ) const  { 
        return time < v.time;    
    } 
}; 

struct CompareUpperBoundValueAndTime { 
    bool operator()( const sValue& v, int time ) const {
        return v.time > time;
    } 

    bool operator()( const sValue& v1, const sValue& v2 ) const { 
        return v1.time > v2.time; 
    }

    bool operator()( int time1, int time2 ) const { 
        return time1 > time2; 
    }   

    bool operator()( int time, const sValue& v ) const  { 
        return time > v.time;    
    } 
}; 

class MyClass {

public:
    MyClass() {
        InsertValues();
    }

       void InsertValues();

       int GetLocationForTime(int time);

       void PrintValueContainer();

private:

    vector<sValue> valueContainer;
};

void MyClass::InsertValues() {
    for(int num = 0; num < 5; num++) {
        sValue temp;
        temp.time = num;
        temp.value = num+1;
        temp.qual = num % 2;
        valueContainer.push_back(temp);
    }
}

void MyClass::PrintValueContainer()
{
    for(int i = 0; i < valueContainer.size(); i++) {
        std::cout << i << ". " << valueContainer[i].time << std::endl;
    }
}




int MyClass::GetLocationForTime(int time)
{
    std::vector< sValue >::iterator lower, upper;
    lower =  std::lower_bound(valueContainer.begin(), valueContainer.end(), time, CompareLowerBoundValueAndTime() );

    upper =  std::upper_bound(valueContainer.begin(), valueContainer.end(), time, CompareUpperBoundValueAndTime() ); // Crashing here.

    std::cout << "Lower bound: " << lower - valueContainer.begin() << std::endl;
    std::cout << "Upper bound: " << upper - valueContainer.begin() << std::endl;

   return lower - valueContainer.begin();
}



int main()
{
    MyClass a;
    a.PrintValueContainer();
    std::cout << "Location received for 2: "  << a.GetLocationForTime(2) << std::endl;
    return 0;
}

Answer 1

lower_bound and upper_bound work on a sorted sequence. The sequence has to be sorted using the same comparing function that you pass to both functions.

When you insert the elements in InsertValues you insert them in ascending order, so your CompareLowerBoundValueAndTime is a correct way to compare them.

But for upper_bound you’re passing a different compare function. Pass CompareLowerBoundValueAndTime() and it should work.

Note that CompareLowerBoundValueAndTime is a misleading name. It should be something along the lines of CompareValueAndTimeAscending.