compare vectors for inequality

GulHK (110)
Hello everyone

I have to compare two vectors (having struct data from two different files) for inequality. The two vectors contain struct type of elements. E-g

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Struct StructVect1
{
	string word_1;
	string word_2;
	string word_3;
	string word_4;
};

Struct StructVect2
{
	string word_1;
	string word_2;
	string word_3;
	string word_4;
};


and suppose vector1 has 10 (struct type) elements in it and vector2 has 5 (struct type) elements in it.

I want to find out all those elements of vector1 the word_1 (e-g vect1[i].word_1) of which is NOT equal to word_4 of any element of the vector2 (e-g vect2[1].word_4, vect2[2].word_4, vect2[3].word_4, vect2[4].word_4).

For example
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if(
vect1[0].word_1 != vect2[0].word_4
vect1[0].word_1 != vect2[1].word_4
vect1[0].word_1 != vect2[2].word_4
vect1[0].word_1 != vect2[3].word_4
)
{
	// push_back vect1[0] to vect3[0]
}


Could you please help.
Duthomhas (13282)
I'm not sure why you have two identical structures with differing names. Just name them the same thing:

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struct FourWords
{
	string word_1;
	string word_2;
	string word_3;
	string word_4;
};

Next, you need a way to compare two structures. Overload the equality operator for that:

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bool operator == ( const FourWords& lhs, const FourWords& rhs )
{
	return	(lhs.word_1 == rhs.word_1)
	and	(lhs.word_2 == rhs.word_2)
	and	(lhs.word_3 == rhs.word_3)
	and	(lhs.word_4 == rhs.word_4);
}

What you want to do is similar. You want to have a little function that will compare your two things properly:

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bool words_1_and_4_not_equal( const FourWords& lhs, const FourWords& rhs )
{
	return lhs.word_1 != rhs.word_4;
}

Once you have that, you only need a little function to do what you want:

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void copy_mismatch(
	const vector <FourWords> & src,
	const vector <FourWords> & cmp,
	      vector <FourWords> & dest )
{
	vector <FourWords> ::const_iterator srciter = src.begin();
	vector <FourWords> ::const_iterator cmpiter = cmp.begin();
	while (srciter != src.end())
	{
		if (words_1_and_4_not_equal( *srciter, *cmpiter ))
		{
			dest.push_back( *srciter );
		}
	}
}
 
 
copy_mismatch( vect1, vect2, vect3 );

You can generalize your code into a generic algorithm, if you like:

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template <
	typename InputIterator1,
	typename InputIterator2,
	typename OutputIterator,
	typename Predicate
	>
OutputIterator
copy_mismatch(
	InputIterator1 first1,
	InputIterator1 last1,
	InputIterator2 first2,
	OutputIterator result,
	Predicate      predicate )
{
	while (first1 != last1)
	{
		if (predicate( *first1, *first2 ))
		{
			*result++ = *first1;
		}
		++first1;
		++first2;
	}
	return result;
}
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#include <iterator>  // for that back_inserter<>

copy_mismatch(
	vect1.begin(),
	vect1.end(),
	vect2.begin(),
	back_inserter( vect3 ),
	words_1_and_4_not_equal
	);
(But you don't have to...)

Anyway, I hope this helps.
GulHK (110)
Duoas! the structures are actually different. They have different number of variables.

variable "word_1" of struct "struct1" contains the following values
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90
85
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85
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87


and variable "word_7" of struct "struct2" contains the following values
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85
90
90


Many thanks. Let me try your solution
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