std::greater in C++ with Examples (original) (raw)

Last Updated : 22 Apr, 2020

The std::greater is a functional object which is used for performing comparisons. It is defined as a Function object class for the greater-than inequality comparison. This can be used for changing the functionality of the given function. This can also be used with various standard algorithms such as sort, priority queue, etc.Header File:

#include <functional.h>

Template Class:

template struct greater;

Parameter: T is a type of the arguments to compare by the functional call.Return Value: It returns boolean variable as shown below:

True: If two element say(a & b) such that a > b.
False: If a < b.

Below is the illustration of std::greater in C++:Program 1:

CPP `

// C++ program to illustrate std::greater

#include #include #include using namespace std;

// Function to print array elements void printArray(int arr[], int n) {

for (int i = 0; i < n; i++) {
    cout << arr[i] << ' ';
}

}

// Driver Code int main() {

int arr[] = { 60, 10, 80, 40, 30,
              20, 50, 90, 70 };
int n = sizeof(arr) / sizeof(arr[0]);

// To sort the array in decreasing order
// use greater <int>() as an third arguments
sort(arr, arr + 9, greater<int>());

// Print array elements
printArray(arr, n);

return 0;

}

Output:

90 80 70 60 50 40 30 20 10

Program 2:

CPP `

// C++ program to illustrate std::greater

#include #include #include using namespace std;

// Function to print elements of priority_queue void showpq(priority_queue<int, vector, greater > pq) { priority_queue<int, vector, greater > g; g = pq;

// While priority_queue is not empty
while (!g.empty()) {

    // Print the top element
    cout << g.top() << ' ';

    // Pop the top element
    g.pop();
}

}

// Driver Code int main() { // priority_queue use to implement // Max Heap, but using function // greater () it implements // Min Heap priority_queue<int, vector, greater > gquiz;

// Inserting Elements
gquiz.push(10);
gquiz.push(30);
gquiz.push(20);
gquiz.push(5);
gquiz.push(1);

// Print elements of priority queue
cout << "The priority queue gquiz is : ";
showpq(gquiz);
return 0;

}

Output:

The priority queue gquiz is : 1 5 10 20 30