## How to compare two vectors for equality element by element in C++?

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Is there any way to compare two vectors?

if (vector1 == vector2) DoSomething();

**Note:** Currently, these vectors are not sorted and contain integer values.

Check `std::mismatch`

method of C++.

comparing vectors has been discussed on **DaniWeb forum** and also **answered**.

Check the below SO post. will helpful for you. they have achieved the same with different-2 method.

Compare two vectors C++

**C++ : How to compare two vectors,** Quickly check if two STL vectors contain same elements or not. Unlike normal C/ C++ arrays, we don't need to do element by element comparison to find if two given vectors contain same elements or not. Check if all elements is equal or not. Unlike normal C/C++ arrays, we don’t need to do element by element comparison to find if two given vectors contain same elements or not. In case of vectors, the operator “==” is overloaded to find the result quickly. Below is an example to demonstrate same.

Your code (`vector1 == vector2`

) is correct C++ syntax. There is an `==`

operator for vectors.

If you want to compare short vector with a portion of a longer vector, you can use the`equal()`

operator for vectors. (documentation here)

Here's an example:

using namespace std; if( equal(vector1.begin(), vector1.end(), vector2.begin()) ) DoSomething();

**Quickly check if two STL vectors contain same elements or not ,** This might fail if elements in second sequence are more than in the first sequence. So it is better to check if size of both vectors are also same. To do: Using the C++ equal() to compare two ranges element by element either for equality or equivalence in a sense specified by a binary predicate in C++ programming To show: How to use the C++ algorithm, equal() to compare two ranges element by element either for equality or equivalence in a sense specified by a binary predicate in C++

According to the discussion here you can directly compare two vectors using

==

if (vector1 == vector2){ //true } else{ //false }

**Check if two vectors are equal or not in C++,** C++ STL algorithm, equal(). #include<vector>. #include<algorithm>. #include< iostream>. usingnamespace std;. // return whether second element is twice of the � Your code (vector1 == vector2) is correct C++ syntax. There is an == operator for vectors. If you want to compare short vector with a portion of a longer vector, you can use the equal () operator for vectors. (documentation here)

**Using the C++ equal() to compare two ranges element by element ,** The equality comparison ( operator== ) is performed by first comparing sizes, and if they match, the elements are compared sequentially using operator==� Queries for elements having values within the range A to B in the given index range using Segment Tree Sum of all Palindrome Numbers present in a Linked list Program to find frequency of each element in a vector using map in C++

If they really absolutely have to remain unsorted (which they really don't.. and if you're dealing with hundreds of thousands of elements then I have to ask why you would be comparing vectors like this), you can hack together a compare method which works with unsorted arrays.

The only way I though of to do that was to create a temporary `vector3`

and pretend to do a `set_intersection`

by adding all elements of `vector1`

to it, then doing a search for each individual element of `vector2`

in `vector3`

and removing it if found. I know that sounds terrible, but that's why I'm not writing any C++ standard libraries anytime soon.

Really, though, just sort them first.

**relational operators (vector) - C++ Reference,** Given two containers c_a and c_b that are not C-arrays, Collections appear to be equal. test.cpp:25: error: in "test_collections_on_c_arrays": check c < a has failed. This is a comparison on the sequences of elements generated by the� Yes, you can use operator== to compare two std::vectors. It will return true only if the vectors are the same size and all elements compare equal.

**Collections comparison - 1.66.0,** With exact decimal arithmetic, C should be equal to exactly 0 . Its small Compare C to 0 for equality. C == 0 Compare the elements of two datetime arrays. When an element x is inserted into L2, you have to check it for equality with all the elements of L1. On each equality with y, increment counters of both elements x and y. When an element x is removed from L2, you have to again compare it with all the elements of L1. On each equality with y from L1, decrement counter of y.

**Determine equality - MATLAB eq ==,** Compare two different character vectors. strcmp returns 0 because s1 and s2 are not equal. Compare each element in two cell arrays of character vectors. Although strcmp shares a name with a C function, it does not follow the C� Create two numeric matrices and compare them for equality. A = zeros (3,3)+1e-20; B = zeros (3,3); tf = isequal (A,B) tf = logical 0. The function returns logical 0 ( false) because the matrices differ by a very small amount and are not exactly equal.

**Compare strings - MATLAB strcmp,** To build logical vectors in R, you'd better know how to compare values, and R smaller than or exactly equal to y Let's assume that you have two vectors containing the number of baskets that Granny <- c(12,4,4,6,9,3) > baskets.of. It depends on what you want to do. identical () will give you simple TRUE/FALSE results, setdiff () will list elements only found in one vector. Using the %in% operator is another good possibility.

##### Comments

- You mean you want to compare
*irrespective*of the order of the elements in the vector? Otherwise, the above code should work. - A simple way to compare if you have two unsorted arrays which you want to check contain exactly the same values, is to
**sort them**, and then use any one of the standard library methods to do a comparison. - If only it were this simple. VS2013 uses
`std::equals`

to implement`==`

, then asserts at runtime because the iterators don't come from the same container(!) You have to set`_ITERATOR_DEBUG_LEVEL=1`

(or`=0`

) on all the projects that use, or might use,`==`

. Arg!! - Does that require the range to be sorted?
`lexicographical_compare`

works here too, and eliminates having to deal with which range is the longer range.- Please post the details of the link you ar reffering here, if that link goes down in future, the whole answer becomes useless.
- Bad answer. You should provide code sample not just links - what if they get down?
- Note that this has no effect on unordered vectors with arbitrary item order: coliru.stacked-crooked.com/a/b66b432234265b7e coliru.stacked-crooked.com/a/66300e8d00a16abf
- std::equal() is also valid for plain arrays, while equality operator is not, for example: int a[1000], b[1000]; if(std::equal(a, a+1000,b)) DoSomething();
- Good answer, except that it encourages bad practice (
`using namespace std`

) instead of using the more clear`std::equal`

. - or may be create two
`set`

objects and compare them? Wouldn't that be easier if it is really required not to touch the vectors. - Depends how quick N lookup-and-remove operations are on a vector (
`N*O(N)`

) versus 2 set constructors sorting N elements (cplusplus.com's reference says "For unsorted sequences, linearithmic (N*logN)..") + a sorted comparison (`O(N)`

).