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Relational Operators on STL Array in C++
• Last Updated : 16 Oct, 2019

The article illustrates the working of the different relational operator on the array STL. The equality comparison ( == ) is performed by comparing the elements sequentially using operator ( == ), stopping at the first mismatch.
The less-than comparison ( < ) or greater-than comparison ( > ) behaves as if using algorithm lexicographical_compare, which compares the elements sequentially using operator () in a reciprocal manner (i.e., checking both a<b and b<a) and stopping at the first occurrence.
The implementation of relational operators on the array help us to compare between the data stored in different arrays.

Equivalent operators : Here are some operators whose work is same.

```  (a != b) is equivalent to !(a == b)
(a > b) equivalent to (b < a)
(a <= b) equivalent to !(b < a)
```

Time Complexity : The time complexity of the above operation is O(n) where n is the size of the array.

Below is the code to illustrate the working of relational operators on array

Program 1: Relational Operator Comparison

 `// array comparisons using relational operators``#include ``using` `namespace` `std;`` ` `int` `main()``{``    ``// declaration of array``    ``array<``int``, 5> a = { 1, 2, 3, 4, 5 };``    ``array<``int``, 5> b = { 1, 2, 3, 4, 5 };``    ``array<``int``, 5> c = { 5, 4, 3, 2, 1 };`` ` `    ``if` `(a >= b) {``        ``cout << ``"a is greater than equal to b\n"``;``    ``}``    ``else` `{``        ``cout << ``"a is neither greater than nor equal to b\n"``;``    ``}`` ` `    ``if` `(b < c) {``        ``cout << ``"b is less than c\n"``;``    ``}``    ``else` `{``        ``cout << ``"b is not lesser than c\n"``;``    ``}``    ``if` `(a >= c) {``        ``cout << ``"a is greater than equal to c\n"``;``    ``}``    ``else` `{``        ``cout << ``"a is neither greater than nor equal to c\n"``;``    ``}`` ` `    ``return` `0;``}`

Output :

```a is greater than equal to b
b is less than c
a is neither greater than nor equal to c
```

Program 2: Relational Operator Equality

 `// CPP program to check for array qualities.``#include ``using` `namespace` `std;`` ` `int` `main()``{``    ``// declaration of array``    ``array<``char``, 5> a = { ``'a'``, ``'b'``, ``'c'``, ``'d'``, ``'e'` `};``    ``array<``char``, 5> b = { ``'e'``, ``'d'``, ``'c'``, ``'b'``, ``'a'` `};``    ``array<``char``, 5> c = { ``'a'``, ``'b'``, ``'c'``, ``'d'``, ``'e'` `};`` ` `    ``if` `(a == b) {``        ``cout << ``"a is  equal to b\n"``;``    ``}``    ``else` `{``        ``cout << ``"a is not equal to b\n"``;``    ``}`` ` `    ``if` `(b != c) {``        ``cout << ``"b is not equal to c\n"``;``    ``}``    ``else` `{``        ``cout << ``"b is equal to c\n"``;``    ``}``    ``if` `(a == c) {``        ``cout << ``"a is equal to c\n"``;``    ``}``    ``else` `{``        ``cout << ``"a is not equal to c\n"``;``    ``}`` ` `    ``return` `0;``}`

Output :

```a is not equal to b
b is not equal to c
a is equal to c
```
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