C++ <deque> - operator< Function

The C++ <deque> operator< function is used to check whether the first deque is less than the second deque or not. It returns true if the first deque is less than the second deque, else returns false. operator< compares elements of deques sequentially and stops comparison after first mismatch.

Syntax

• C++98
• C++11

template <class T, class Alloc>
bool operator< (const deque<T,Alloc>& lhs, const deque<T,Alloc>& rhs);

template <class T, class Alloc>
bool operator< (const deque<T,Alloc>& lhs, const deque<T,Alloc>& rhs);

Parameters

Return Value

Returns true if the contents of lhs are lexicographically less than the contents of rhs, else returns false.

Time Complexity

Linear i.e, Θ(n).

Example:

In the example below, the operator< function is used to check whether the first deque is less than the second deque or not.

#include <iostream>
#include <deque>
using namespace std;
 
int main (){
  deque<int> dq1 {10, 20, 30};
  deque<int> dq2 {10, 20, 30};
  deque<int> dq3 {40, 50, 60};

  if (dq1 < dq2)
    cout<<"dq1 is less than dq2.\n";
  else
    cout<<"dq1 is not less than dq2.\n";

  if (dq1 < dq3)
    cout<<"dq1 is less than dq3.\n";
  else
    cout<<"dq1 is not less than dq3.\n";
    
  return 0;
}

The output of the above code will be:

dq1 is not less than dq2.
dq1 is less than dq3.