Create N_Queen's_position_Printing_in_grid_style

Algorithms/C++/C++/N_Queen's_position_Printing_in_grid_style(All_Possible_Soln).cpp

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+// N chess queens on an N×N chessboard so that no two queens attack each other
+
+//By Soumyadeep Pal
+#include <iostream>
+using namespace std;
+
+//For counting total possible soln
+static int count;
+
+// Queen's position Printing in grid style
+void print_Grid_style(int userRows, int **arr)
+{
+    int userColumns = userRows;
+    cout << "\n";
+    cout << " ";
+    int i, j;
+    cout << "\n";
+    for (i = 0; i <= 2 * userRows; i++)
+    {
+        if (i % 2 != 0)
+            cout << " ";
+        for (j = 0; j <= 2 * userColumns; j++)
+        {
+            if (i % 2 == 0)
+            {
+                if (j == 0)
+                    cout << " ";
+                if (j % 2 == 0)
+                    cout << " ";
+                else
+                    cout << "---";
+            }
+            else
+            {
+                if (j % 2 == 0)
+                    cout << "|";
+                else
+                {
+                    cout << " ";
+                    if (arr[i / 2][j / 2] == 1)
+                        cout << "Q"; //just replace Q to 1 &
+                    else
+                        cout << " "; // replace space to 0 if u want to print in 0-1 format
+                    cout << " ";
+                }
+            }
+        }
+        cout << "\n";
+    }
+}
+
+bool check_pos(int **arr, int x, int y, int n)
+{
+    for (int row = 0; row < n; row++)
+    {
+        if (arr[row][y] == 1)
+        {
+            return false;
+        }
+    }
+
+    //for upper left diagonal
+    int row = x, col = y;
+    while (row >= 0 && col >= 0)
+    {
+        if (arr[row][col] == 1)
+        {
+            return false;
+        }
+        row--, col--;
+    }
+
+    //for upper right diagonal
+    row = x, col = y;
+    while (row >= 0 && col < n) //coz queen can't be placed outside
+    {
+        if (arr[row][col] == 1)
+        {
+            return false;
+        }
+        row--, col++;
+    }
+    return true;
+}
+bool nqueen(int **arr, int x, int n) //not required to pass y & prev column coz we already placed our queen on the next row
+{
+    //Base case:
+    if (x >= n)
+    {
+        print_Grid_style(n, arr);
+        count++;
+    }
+
+    for (int col = 0; col < n; col++)
+    {
+        if (check_pos(arr, x, col, n))
+        {
+            arr[x][col] = 1;
+
+            if (nqueen(arr, x + 1, n))
+            {
+                return true;
+            }
+            //If placed queen clashes with already placed queens then remove queen from board and put 0 in those position
+            arr[x][col] = 0;
+        }
+    }
+    return false;
+}
+
+int main()
+{
+    cout << "Enter the number of Queens: ";
+    int n;
+    cin >> n;
+    int **arr = new int *[n];
+
+    for (int i = 0; i < n; i++)
+    {
+
+        arr[i] = new int[n];
+    }
+
+    for (int i = 0; i < n; i++)
+    {
+        for (int j = 0; j < n; j++)
+        {
+
+            arr[i][j] = 0;
+        }
+    }
+    if (n > 3)
+    {
+        nqueen(arr, 0, n);
+    }
+    cout << "\nPossible solutions exist for an " << n << "-queen problem: " << count << "\n";
+    return 0;
+}