# C++ Notes: Example - Battleship ver 3a

This is working version of a one-dimensional Battleship game. It places multiple ships on a one-dimensional grid (the Suez Canal).

      1
      2
      3
      4
      5
      6
      7
      8
      9
     10
     11
     12
     13
     14
     15
     16
     17
     18
     19
     20
     21
     22
     23
     24
     25
     26
     27
     28
     29
     30
     31
     32
     33
     34
     35
     36
     37
     38
     39
     40
     41
     42
     43
     44
     45
     46
     47
     48
     49
     50
     51
     52
     53
     54
     55
     56
     57
     58
     59
     60
     61
     62
     63
     64
     65
     66
     67
     68
     69
     70
     71
     72
     73
     74
     75
     76
     77
     78
     79
     80
     81
     82
     83
     84
     85
     86
     87
     88
     89
     90
     91
     92
     93
     94
     95
     96
     97
     98
     99
    100
    101
    102
    103
    104
    105
    106
    107
    108
    109
    110
    111
    112
    113
    114
    115
    116
    117
    118
    119
    120
    121
    122
    123
    124
    125
    126
    127
    128
    129
    130
    131
    132
    133
    134
    135
    136
    137
    138
    139
    140
    141
    142
    143
    144
    145
    146
    147
    148
    149
    150
    151
    152
    153
    154
    155
    156
    157
    158
    159
    160
    161
    162
    163
    164
    165
    166
    167
    168
    169
    170
    171
    172
    173
    174
    175
    176
    177
    178
    179
    180
    181
    182
    183
    184
    185
    186
    187
    //  battleship3a/main.cpp -- Version 3a of Battleship game.
    //  Fred Swartz, 2003-11-25

    // This second version adds the following to version 2.
    //  * Places multiple ships randomly on grid.
    //
    // FUNCTIONALITY TO BE ADDED
    //  * Make it two-dimensional.
    //  * Should be a developer command to display where ships are.
    //
    // USER INTERFACE
    //  * Not robust - crashes if bombing coordinate missing.

    //==================================================== includes
    #include <iostream>
    #include <iomanip>
    #include <string>
    #include <ctime>    // For time()
    #include <cstdlib>  // For srand() and rand()
    using namespace std;

    //========================================= global declarations
    // Damage enum defines possible values at each grid point.
    enum Damage {WATER_UNBOMBED, WATER_BOMBED,
                 SHIP_UNBOMBED , SHIP_BOMBED};

    // The display array defines what to display for
    //     each of the Damage enum values.  Changes to the
    //     Damage enum require this to be changed also.
    const char display[] = {'-', 'O', '-', 'X'};

    const  int SHIP_SIZE = 3;
    const  int NUMBER_OF_SHIPS = 4;
    const  int CANAL_LENGTH = 24;   // Width of the grid.
    Damage grid[CANAL_LENGTH];      // Records status of every grid cell.

    //================================================== prototypes
    void dropBomb(int coord);
    void executeCommand(char cmd);
    void findOpenWater(int positions[], int& number);
    void initGrid();
    bool isGameOver();
    void printGrid();

    //======================================================== main
    int main() {

        srand(time(0));  // Initialize random number generator

        cout << "You are to find and bomb ships in the Suez Canal." << endl;
        cout << "Each ship is " << SHIP_SIZE << " units long." << endl;
        cout << "Use the b command and follow it with a coordinate to drop a bomb." << endl;

        char ans;
        do {
            initGrid();  // Randomly place ships on the grid.
            printGrid();

            char commandCode;
            while (cin >> commandCode) {

                executeCommand(commandCode);

                if (isGameOver()) {
                    cout << "I surrender." << endl;
                    break;
                }
            }
            cout << "Do you want to play again? (y/n) ";
            cin >> ans;
        } while (ans == 'y');

        return 0;
    }//end main

    //======================================================= executeCommand
    void executeCommand(char cmd) {
        switch (cmd) {

            case 'q':           // quit
                exit(0);
                break;

            case 'b':           // bomb
                int loc;
                cin >> loc;
                if (loc>=0 && loc<CANAL_LENGTH) {
                    dropBomb(loc);
                } else {
                    cout << "Bombing coordinate must be between 0 and " << CANAL_LENGTH-1 << endl;
                }
                printGrid();
                break;

            default:            // error
                cerr << "Bad input " << cmd << endl;
                break;
        }
    }

    //======================================================= dropBomb
    void dropBomb(int coord) {
        switch (grid[coord]) {

        case WATER_UNBOMBED:
              grid[coord] = WATER_BOMBED;
              break;

        case SHIP_UNBOMBED:
              grid[coord] = SHIP_BOMBED;
              break;
        }
        return;
    }

    //======================================================= initGrid
    // initGrid() places random ships on the grid.
    void initGrid() {
        //-- Initialize the grid to empty water
        for (int i=0; i<CANAL_LENGTH; i++) {
            grid[i] = WATER_UNBOMBED;
        }

        //-- Make a list of where ships could be placed.
        int openWaterPositions[CANAL_LENGTH];
        int howManyPositions;  // number of elements in openWaterPositions

        for (int shipNum=0; shipNum < NUMBER_OF_SHIPS; shipNum++) {
            findOpenWater(openWaterPositions, howManyPositions);  // sets both parameters
            if (howManyPositions == 0) {
                break;  // we're done even if we didn't put all ships in water.
            }
            //-- Choose one of the open water positions randomly.
            int onePosition = rand() % howManyPositions;
            int start = openWaterPositions[onePosition];

            //-- Put a ship starting from there to the right.
            for (int pos=start; pos<start+SHIP_SIZE; pos++) {
                grid[pos] = SHIP_UNBOMBED;
            }
        }
    }

    //====================================================== findOpenWater
    void findOpenWater(int positions[], int& number) {
        number = 0;  // Start assuming no open water found.
        int consecutiveWater = 0;
        for (int i=CANAL_LENGTH-1; i>=0; i--) {
            if (grid[i]==WATER_UNBOMBED) {
                consecutiveWater++;
                if (consecutiveWater > SHIP_SIZE) {
                    //-- record this as a possible position.
                    positions[number] = i;
                    number++;
                }
            } else {
                consecutiveWater = 0;
            }
        }
    }

    //====================================================== printGrid
    void printGrid() {
        cout << endl;
        for (int i=0; i<CANAL_LENGTH; i++) {
            cout << " " << display[grid[i]];
        }
        cout << endl;

        //-- Print coordinates.
        for (int coord=0; coord<CANAL_LENGTH; coord++) {
            cout << setw(2) << coord;
        }
        cout << endl << endl;
    }

    //====================================================== isGameOver
    bool isGameOver() {
        for (int coord=0; coord<CANAL_LENGTH; coord++) {
            if (grid[coord] == SHIP_UNBOMBED) {
                return false;
            }
        }
        return true;
    }
The text from the above example can be selected, copied, and pasted into an editor.