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Add files from sample and basic README.

nqueens/NQueens.cpp

+// Example of solution to N-Queens problem
+// Dr. David Paoletti
+
+#include <iostream>
+#include <string>
+#include "NQueens.hpp"
+using namespace std;
+
+const bool NQueens::AVAILABLE = true;
+
+// Construct the "available" 
+NQueens::NQueens(unsigned n) : squares{n}, solutions{0}, tried{0},
+    positionInRow(n, -1), column(n, AVAILABLE),
+    leftDiagonal(2 * n - 1, AVAILABLE), rightDiagonal(2 * n - 1, AVAILABLE) {
+} // NQueens constructor
+
+
+// Solve this board (public member function)
+// If display == true, display each board as a solution is found
+void NQueens::solve(bool display) {
+    putQueen(0, display);
+} // NQueens::solve()
+
+
+// Place a queen in row
+// If display == true, display each board as a solution is found
+void NQueens::putQueen(unsigned row, bool display) {
+    // Check every column within this row
+    for (unsigned col = 0; col < squares; col++) {
+        // Check if proposed placement is promising
+        if (   column[col] == AVAILABLE
+            && leftDiagonal[row + col] == AVAILABLE
+            && rightDiagonal[row - col + (squares - 1)] == AVAILABLE) {
+            positionInRow[row] = col;
+            column[col] = !AVAILABLE;
+            leftDiagonal[row + col] = !AVAILABLE;
+            rightDiagonal[row - col + (squares - 1)] = !AVAILABLE;
+
+            // Check for solution
+            if (row == squares - 1) {
+                solutions++;
+                if (display)
+                {
+                    cout << "Solution found:\n";
+                    displayBoard();
+                } // if
+            } // if
+            else
+                putQueen(row + 1, display);
+
+            // Undo this move and thus backtrack
+            column[col] = AVAILABLE;
+            leftDiagonal[row + col] = AVAILABLE;
+            rightDiagonal[row - col + (squares - 1)] = AVAILABLE;
+        } // if
+        tried++;
+    } // for
+}  // NQueens::putQueen()
+
+
+// Send the board to the screen
+void NQueens::displayBoard() {
+    string bar = "+";
+
+    for (unsigned col = 0; col < squares; col++)
+        bar += "---+";
+
+    for (unsigned row = 0; row < squares; row++) {
+        cout << "     " << bar << endl << "    ";
+
+        for (unsigned col = 0; col < squares; col++) {
+            cout << " | ";
+            if (positionInRow[row] == col)
+                cout << "Q";
+            else
+                cout << " ";
+        } // for col
+        cout << " |" << endl;
+    } // for row
+
+    cout << "     " << bar << endl;
+    cout << endl;
+} // NQueens::displayBoard()
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nqueens/NQueens.hpp

+// Example of solution to N-Queens problem
+// Dr. David Paoletti
+
+#ifndef NQUEENS_HPP
+#define NQUEENS_HPP
+
+#include <vector>
+using namespace std;
+
+
+class NQueens {
+private:
+    unsigned squares;
+    unsigned long long solutions, tried;
+    vector<int> positionInRow;
+    vector<bool> column, leftDiagonal, rightDiagonal;
+
+    static const bool AVAILABLE;
+
+    void putQueen(unsigned row, bool display = true);
+    void displayBoard();
+
+public:
+    NQueens(unsigned n);
+    void solve(bool display = true);
+    unsigned long long getSolutions() const { return solutions; }
+    unsigned long long getTried() const { return tried; }
+}; // NQueens
+
+#endif // NQUEENS_HPP
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nqueens/n_queens_demo.cpp

+// Example of solution to N-Queens problem
+// Dr. David Paoletti
+
+#include <iostream>
+#include <cmath>
+#include "NQueens.hpp"
+using namespace std;
+
+
+int main() {
+    unsigned n;
+    char display;
+    double perms, savings;
+
+    cout << "Enter number of queens: ";
+    cin >> n;
+    cout << "Display results? ";
+    cin >> display;
+    display = toupper(display);
+
+    NQueens board(n);
+    board.solve(display == 'Y');
+    perms = pow(n, n);
+    savings = (1 - (double)board.getTried() / perms) * 100;
+
+    cout << "There were " << board.getSolutions() << " solutions\n";
+    cout << board.getTried() << " branches were explored out of ";
+    cout << perms << " possible permutations,\n";
+    cout << "A savings of " << savings << "%\n";
+
+    return 0;
+} // main()
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