C++ Deque Library - operator< Function


The C++ function std::deque::operator< tests whether first deque is less than other or not.


Following is the declaration for std::deque::operator< function form std::deque header.


template <class T, class Alloc>
bool operator< (const deque<T,Alloc>& first, const deque<T,Alloc>& second);


  • first − First deque object.

  • second − Second deque object of same type.

Return value

Returns true if first deque is less than second otherwise false.


This member function never throws exception.

Time complexity

Linear i.e. O(n)


The following example shows the usage of std::deque::operator< function.

#include <iostream>
#include <deque>

using namespace std;

int main(void) {

   deque<int> d1 = {1, 2, 3};
   deque<int> d2 = {1, 2, 3, 4, 5};

   if (d1 < d2)
      cout << "Deque d1 is less than d2." << endl;

   d2.assign(1, 1);

   if (!(d1 < d2))
      cout << "Deque d1 is not less than d2." << endl;

   return 0;

Let us compile and run the above program, this will produce the following result −

Deque d1 is less than d2.
Deque d1 is not less than d2.
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