Added code for n-queen problem (practical-5).

Codes/Code-A5.py

@@ -0,0 +1,61 @@
+# Practical-A5 (N-Queen)
+
+"""
+THIS CODE HAS BEEN TESTED AND IS FULLY OPERATIONAL.
+
+Problem Statement: Design n-Queens matrix having first Queen placed. Use backtracking to place remaining Queens to generate the final n-queen‘s matrix.
+
+Code from DesignAndAnalysisOfAlgorithms (SPPU - Final Year - Computer Engineering - Content) repository on KSKA Git: https://git.kska.io/sppu-be-comp-content/DesignAndAnalysisOfAlgorithms/
+"""
+
+# BEGINNING OF CODE
+def placeQueens(i, cols, leftDiagonal, rightDiagonal, cur):
+    n = len(cols)
+
+    if i == n:
+        return True
+
+    for j in range(n):
+        if cols[j] or rightDiagonal[i + j] or leftDiagonal[i - j + n - 1]:
+            continue
+
+        cols[j] = 1 
+        rightDiagonal[i + j] = 1
+        leftDiagonal[i - j + n - 1] = 1
+        cur.append(j)
+
+        if placeQueens(i + 1, cols, leftDiagonal, rightDiagonal, cur):
+            return True
+
+        cur.pop()
+        cols[j] = 0
+        rightDiagonal[i + j] = 0
+        leftDiagonal[i - j + n - 1] = 0
+
+    return False
+
+def nQueen(n):
+    cols = [0] * n
+    leftDiagonal = [0] * (n * 2)
+    rightDiagonal = [0] * (n * 2)
+    cur = []
+    board = [['.' for _ in range(n)] for _ in range(n)]
+
+    if placeQueens(0, cols, leftDiagonal, rightDiagonal, cur):
+        for i in range(n):
+            board[i][cur[i]] = 'Q'
+        return board
+    else:
+        return None
+
+def printBoard(board):
+    if board:
+        for row in board:
+            print(" ".join(row))
+    else:
+        print("No solution exists.")
+
+n = int(input("Enter the number of queens:\t"))
+board = nQueen(n)
+printBoard(board)
+# END OF CODE