8 puzzle problem using Prolog

				
					#include <bits/stdc++.h>

using namespace std;
#define N 3
struct Node {
  Node * parent;
  int mat[N][N];
  int x, y;
  int cost;
  int level;
};
int printMatrix(int mat[N][N]) {
  for (int i = 0; i < N; i++) {
    for (int j = 0; j < N; j++)
      printf("%d ", mat[i][j]);
    printf("\n");
  }
}
Node * newNode(int mat[N][N], int x, int y, int newX,
  int newY, int level, Node * parent) {
  Node * node = new Node;
  node -> parent = parent;
  memcpy(node -> mat, mat, sizeof node -> mat);
  swap(node -> mat[x][y], node -> mat[newX][newY]);
  node -> cost = INT_MAX;
  node -> level = level;
  node -> x = newX;
  node -> y = newY;
  return node;
}
int row[] = { 1, 0, -1, 0 };
int col[] = { 0, -1, 0, 1 };
int calculateCost(int initial[N][N], int final[N][N]) {
  int count = 0;
  for (int i = 0; i < N; i++)
    for (int j = 0; j < N; j++)
      if (initial[i][j] && initial[i][j] != final[i][j])
        count++;
  return count;
}
int isSafe(int x, int y) {
  return (x >= 0 && x < N && y >= 0 && y < N);
}
void printPath(Node * root) {
  if (root == NULL)
    return;
  printPath(root -> parent);
  printMatrix(root -> mat);
  printf("\n");
}
struct comp {
  bool operator()(const Node * lhs,
    const Node * rhs) const {
    return (lhs -> cost + lhs -> level) > (rhs -> cost + rhs -> level);
  }
};
void solve(int initial[N][N], int x, int y,
  int final[N][N]) {
  priority_queue < Node * , std::vector < Node * > , comp > pq;
  Node * root = newNode(initial, x, y, x, y, 0, NULL);
  root -> cost = calculateCost(initial, final);
  pq.push(root);
  while (!pq.empty()) {
    Node * min = pq.top();
    pq.pop();
    if (min -> cost == 0) {
      printPath(min);
      return;
    }
    for (int i = 0; i < 4; i++) {
      if (isSafe(min -> x + row[i], min -> y + col[i])) {
        Node * child = newNode(min -> mat, min -> x,
          min -> y, min -> x + row[i],
          min -> y + col[i],
          min -> level + 1, min);
        child -> cost = calculateCost(child -> mat, final);
        pq.push(child);
      }
    }
  }
}
int main() {
  int initial[N][N] = {
    {1, 2, 3},
    {5, 6, 0},
    {7, 8, 4}
  };
  int final[N][N] = {
    {1, 2, 3},
    {5, 8, 6},
    {0, 7, 4}
  };
  int x = 1, y = 2;
  solve(initial, x, y, final);
  return 0;
}