Problem 11

#include <iostream>
#include <sstream>
using namespace std;

#define CLM 20
#define ROW 20
#define MAT "\
08 02 22 97 38 15 00 40 00 75 04 05 07 78 52 12 50 77 91 08 \
49 49 99 40 17 81 18 57 60 87 17 40 98 43 69 48 04 56 62 00 \
81 49 31 73 55 79 14 29 93 71 40 67 53 88 30 03 49 13 36 65 \
52 70 95 23 04 60 11 42 69 24 68 56 01 32 56 71 37 02 36 91 \
22 31 16 71 51 67 63 89 41 92 36 54 22 40 40 28 66 33 13 80 \
24 47 32 60 99 03 45 02 44 75 33 53 78 36 84 20 35 17 12 50 \
32 98 81 28 64 23 67 10 26 38 40 67 59 54 70 66 18 38 64 70 \
67 26 20 68 02 62 12 20 95 63 94 39 63 08 40 91 66 49 94 21 \
24 55 58 05 66 73 99 26 97 17 78 78 96 83 14 88 34 89 63 72 \
21 36 23 09 75 00 76 44 20 45 35 14 00 61 33 97 34 31 33 95 \
78 17 53 28 22 75 31 67 15 94 03 80 04 62 16 14 09 53 56 92 \
16 39 05 42 96 35 31 47 55 58 88 24 00 17 54 24 36 29 85 57 \
86 56 00 48 35 71 89 07 05 44 44 37 44 60 21 58 51 54 17 58 \
19 80 81 68 05 94 47 69 28 73 92 13 86 52 17 77 04 89 55 40 \
04 52 08 83 97 35 99 16 07 97 57 32 16 26 26 79 33 27 98 66 \
88 36 68 87 57 62 20 72 03 46 33 67 46 55 12 32 63 93 53 69 \
04 42 16 73 38 25 39 11 24 94 72 18 08 46 29 32 40 62 76 36 \
20 69 36 41 72 30 23 88 34 62 99 69 82 67 59 85 74 04 36 16 \
20 73 35 29 78 31 90 01 74 31 49 71 48 86 81 16 23 57 05 54 \
01 70 54 71 83 51 54 69 16 92 33 48 61 43 52 01 89 19 67 48 \
"

enum ORIENTATION
{
    UP = 0,
    DOWN,
    LEFT,
    RIGHT,
    LEFT_UP,
    RIGHT_UP,
    RIGHT_DOWN,
    LEFT_DOWN,
    ORI_NUM
};

int
main(int argc, char **argv)
{
    istringstream is(MAT);
    int table[ROW][CLM];
    
    for (int y = 0; y < ROW; y++)
    {
        for (int x = 0; x < CLM; x++)
        {
            is >> table[y][x];
        }
    }

    int mv[8][2] = { // 移動方向
        { 0, -1},    // 上
        { 0,  1},    // 下
        {-1,  0},    // 左
        { 1,  0},    // 右
        {-1, -1},    // 左上
        { 1, -1},    // 右上
        { 1,  1},    // 右下
        {-1,  1}     // 左下
    };
    int max = -1;

    for (int y = 0; y < ROW; y++)
    {
        for (int x = 0; x < CLM; x++)
        {
            for (int ori = 0; ori < ORI_NUM; ori++)
            {
                // はみ出ないように
                bool f = false;
                switch (ori)
                {
                case UP:
                    if (y-3 < 0)
                        f = true;
                    break;
                case DOWN:
                    if (ROW <= y+3)
                        f = true;
                    break;
                case LEFT:
                    if (x-3 < 0)
                        f = true;
                    break;
                case RIGHT:
                    if (CLM <= x+3)
                        f = true;
                    break;
                case LEFT_UP:
                    if (x-3 < 0 || y-3 < 0)
                        f = true;
                    break;
                case RIGHT_UP:
                    if (CLM <= x+3 || y-3 < 0)
                        f = true;
                    break;
                case RIGHT_DOWN:
                    if (CLM <= x+3 || ROW <= y+3)
                        f = true;
                    break;
                case LEFT_DOWN:
                    if (x-3 < 0 || ROW <= y+3)
                        f = true;
                    break;
                }
                if (f)
                    continue;


                int pr = 1;
                for (int i = 0; i < 4; i++)
                {
                    pr *= table[y+mv[ori][1]*i][x+mv[ori][0]*i];
                }

                if (max < pr)
                {
                    max = pr;
                }
            }
        }
    }    

    cout << max << endl;

    return 0;
}