#include iostream#include algorithmusing namespace std;struct node int x y; node next;;bool includenode n int x int y node p = &n; while p != nullptr if p-x == x && p-y == y retu

The given code is an implementation of a breadth-first search algorithm to find the number of possible paths from one point (x1, y1) to another point (x2, y2) on a 2D grid.

The node struct represents a point on the grid, with x and y coordinates, and a next pointer to the next node in the path.

The include function checks if a given point (x, y) is included in the path represented by a linked list of nodes. It iterates through the list and returns true if the point is found.

The validPosition function checks if a given point (x, y) is a valid position on the grid, i.e., within the bounds of the grid defined by n and m.

The appendNode function appends a new node to the path represented by the linked list. It creates a new node with the coordinates of the current node plus the given adjX and adjY values, and updates the next pointer of the current node to point to the new node.

The num function takes the dimensions of the grid (n and m), the starting point (x1 and y1), and the ending point (x2 and y2). It initializes a linked list with the starting point and uses a breadth-first search algorithm to explore all possible paths.

In each iteration of the do-while loop, it checks if the current node is the ending point. If so, it increments the ans variable to count the number of paths found. Otherwise, it checks all possible adjacent positions from the current node and appends new nodes to the path if they are valid positions and not already included in the path.

After each iteration, it updates the front pointer to the last node in the path and continues until all possible paths have been explored.

Finally, it returns the value of ans, which represents the number of paths found from the starting point to the ending point on the grid.

The main function calls the num function with specific arguments and prints the result