1 files changed, 282 insertions, 0 deletions
diff --git a/challenge-118/paulo-custodio/cpp/ch-2.cpp b/challenge-118/paulo-custodio/cpp/ch-2.cpp
new file mode 100644
index 0000000000..e82e6b045f
--- /dev/null
+++ b/challenge-118/paulo-custodio/cpp/ch-2.cpp
@@ -0,0 +1,282 @@
+/*
+Challenge 118
+
+TASK #2 - Adventure of Knight
+Submitted by : Cheok - Yin Fung
+A knight is restricted to move on an 8×8 chessboard.The knight is denoted by
+N and its way of movement is the same as what it is defined in Chess.
+* represents an empty square. x represents a square with treasure.
+
+The Knight’s movement is unique.It may move two squares vertically and one
+square horizontally, or two squares horizontally and one square vertically
+(with both forming the shape of an L).
+
+There are 6 squares with treasures.
+
+Write a script to find the path such that Knight can capture all treasures.
+The Knight can start from the top - left square.
+
+  a b c d e f g h
+8 N * * * * * * * 8
+7 * * * * * * * * 7
+6 * * * * x * * * 6
+5 * * * * * * * * 5
+4 * * x * * * * * 4
+3 * x * * * * * * 3
+2 x x * * * * * * 2
+1 * x * * * * * * 1
+  a b c d e f g h
+
+https://en.m.wikipedia.org/wiki/Knight%27s_tour
+*/
+
+#include <cassert>
+#include <cctype>
+#include <cstring>
+#include <iostream>
+#include <string>
+#include <vector>
+using namespace std;
+
+#define NROWS       8
+#define NCOLS       8
+#define MAX_MOVES   8
+
+struct Board {
+    Board() {
+        clear();
+    }
+
+    void clear() {
+        memset(cells, 0, NROWS);
+    }
+
+    bool empty() const {
+        for (int i = 0; i < NROWS; i++)
+            if (cells[i] != 0)
+                return false;
+        return true;
+    }
+
+    void set(int row, int col) {
+        assert(row >= 0 && row < NROWS);
+        assert(col >= 0 && col < NCOLS);
+        int mask = 1 << col;
+        cells[row] |= mask;
+    }
+
+    void reset(int row, int col) {
+        assert(row >= 0 && row < NROWS);
+        assert(col >= 0 && col < NCOLS);
+        int mask = 1 << col;
+        cells[row] &= ~mask;
+    }
+
+    bool peek(int row, int col) const {
+        assert(row >= 0 && row < NROWS);
+        assert(col >= 0 && col < NCOLS);
+        int mask = 1 << col;
+        return (cells[row] & mask) == 0 ? false : true;
+    }
+
+    char cells[NROWS];
+};
+
+struct Game {
+    Game() {
+        clear();
+    }
+
+    void clear() {
+        row = col = 0;
+        visited.clear();
+        treasure.clear();
+        path.clear();
+    }
+
+    void set_visited(int row, int col) {
+        visited.set(row, col);
+    }
+
+    bool peek_visited(int row, int col) const {
+        return visited.peek(row, col);
+    }
+
+    void set_treasure(int row, int col) {
+        treasure.set(row, col);
+    }
+
+    void clear_treasure(int row, int col) {
+        treasure.reset(row, col);
+    }
+
+    bool peek_treasure(int row, int col) const {
+        return treasure.peek(row, col);
+    }
+
+    bool done() const {
+        return treasure.empty();
+    }
+
+    void move(int row, int col) {
+        set_visited(row, col);
+        clear_treasure(row, col);
+        path += 'a' + col;
+        path += to_string(NROWS - row);
+        path += " ";
+        this->row = row;
+        this->col = col;
+    }
+
+    friend ostream& operator<<(ostream& os, const Game& game) {
+        os << "  a b c d e f g h" << endl;
+        for (int row = 0; row < NROWS; row++) {
+            os << NROWS - row;
+            for (int col = 0; col < NCOLS; col++) {
+                if (game.peek_treasure(row, col))
+                    os << " x";
+                else if (game.row == row && game.col == col)
+                    os << " N";
+                else if (game.peek_visited(row, col))
+                    os << " .";
+                else
+                    os << " *";
+            }
+            os << " " << NROWS - row << endl;
+        }
+        os << "  a b c d e f g h" << endl;
+        os << endl << "> " << game.path << endl;
+        return os;
+    }
+
+    void parse_header() {
+        string line;
+        if (!getline(cin, line)) {
+            cerr << "expected header or footer" << endl;
+            exit(EXIT_FAILURE);
+        }
+        const char* p = line.c_str();
+        while (*p && isspace(*p)) p++;
+        if (strncmp(p, "a b c d e f g h", 15) != 0) {
+            cerr << "invalid header or footer" << endl;
+            exit(EXIT_FAILURE);
+        }
+    }
+
+    void parse_row(int row) {
+        string line;
+        if (!getline(cin, line)) {
+            cerr << "expected row " << NROWS - row << endl;
+            exit(EXIT_FAILURE);
+        }
+        const char* p = line.c_str();
+        while (*p && isspace(*p)) p++;
+        if (!isdigit(*p) || *p - '0' != NROWS - row) {
+            cerr << "invalid row " << NROWS - row << endl;
+            exit(EXIT_FAILURE);
+        }
+        p++;
+        for (int col = 0; col < NCOLS; col++) {
+            while (*p && isspace(*p)) p++;
+            switch (*p) {
+                case 'N': move(row, col); break;
+                case 'x': set_treasure(row, col); break;
+                case '*': break;
+                default:
+                    cerr << "invalid row " << NROWS - row << endl;
+                    exit(EXIT_FAILURE);
+            }
+            p++;
+        }
+    }
+
+    void parse() {
+        clear();
+        parse_header();
+        for (int row = 0; row < NROWS; row++)
+            parse_row(row);
+        parse_header();
+    }
+
+    int row{ 0 }, col{ 0 };
+    Board visited, treasure;
+    string path;
+};
+
+struct Move {
+    int row, col, num_moves;
+
+    Move(int row = 0, int col = 0, int num_moves = 0)
+        : row(row), col(col), num_moves(num_moves) {}
+};
+
+void try_move(vector<Move>& moves, Game& game, int nrow, int ncol) {
+    if (nrow < 0 || nrow >= NROWS) return;
+    if (ncol < 0 || ncol >= NCOLS) return;
+    if (game.peek_visited(nrow, ncol)) return;
+
+    moves.push_back(Move(nrow, ncol, 0));
+}
+
+void try_num_moves(vector<Move>& moves, Game& game, int row, int col) {
+    moves.clear();
+    try_move(moves, game, row + 2, col + 1);
+    try_move(moves, game, row + 2, col - 1);
+    try_move(moves, game, row - 2, col + 1);
+    try_move(moves, game, row - 2, col - 1);
+    try_move(moves, game, row + 1, col + 2);
+    try_move(moves, game, row - 1, col + 2);
+    try_move(moves, game, row + 1, col - 2);
+    try_move(moves, game, row - 1, col - 2);
+}
+
+vector<Move> next_moves(Game& game) {
+    vector<Move> moves;
+
+    // try first step
+    try_num_moves(moves, game, game.row, game.col);
+
+    // for each target location count number of further steps
+    int min_moves = MAX_MOVES + 1;
+    for (size_t i = 0; i < moves.size(); i++) {
+        vector<Move> temp_moves;
+        try_num_moves(temp_moves, game, moves[i].row, moves[i].col);
+        moves[i].num_moves = temp_moves.size();
+        if (min_moves > moves[i].num_moves) min_moves = moves[i].num_moves;
+    }
+
+    // remove all moves with targets > min_moves
+    size_t j = 0;
+    for (size_t i = 0; i < moves.size(); i++) {
+        if (moves[i].num_moves == min_moves)
+            moves[j++] = moves[i];
+    }
+    moves.resize(j);
+
+    return moves;
+}
+
+void solve(Game& solution, Game& game) {
+    if (game.done()) {
+        if (solution.path.size() == 0 || solution.path.size() > game.path.size()) {
+            // cout << game;
+            solution = game;
+        }
+    }
+    else {
+        vector<Move> moves = next_moves(game);
+        for (size_t i = 0; i < moves.size(); i++) {
+            Game new_game = game;
+            new_game.move(moves[i].row, moves[i].col);
+            solve(solution, new_game);
+        }
+    }
+}
+
+int main(void) {
+    Game game, solution;
+    game.parse();
+
+    solve(solution, game);
+    cout << solution.path << endl;
+}