Project Euler #11 - Largest product in a grid

In the 20×20 grid below, four numbers along a diagonal line have been marked in red.

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

The product of these numbers is 26 × 63 × 78 × 14 = 1788696.

What is the greatest product of four adjacent numbers in the same direction (up, down, left, right, or diagonally) in the 20×20 grid?

출처: https://projecteuler.net/

20 * 20 숫자가 주어졌을 때 수평, 수직, 또는 대각선 방향으로 연속된 숫자 네 개의 곱 중 최대값을 구하는 문제입니다.

완전 탐색으로 풀 수 있는 문제네요.

my solving

c++

#include <iostream>
#include <fstream>
#include <algorithm>
using namespace std;
typedef long long ll;
 
int numbers[20][20] = { 0, };
 
int getNumber(int low, int column)
{
    if (column < 0 || column > 19 || low < 0 || low > 19)
        return 0;
    return numbers[low][column];
}
 
 
int main() 
{
    ifstream fin("input.in");
    ll ret = 0;
 
    for (int row = 0; row < 20; row++)
    {
        for (int column = 0; column < 20; column++)
        {
            int num;
            fin >> num;
            numbers[row][column] = num;
        }
    }
 
    for (int row = 0; row < 20; row++)
    {
        for (int column = 0; column < 20; column++)
        {
            ll product = getNumber(row, column) * getNumber(row, column + 1) * getNumber(row, column + 2) * getNumber(row, column + 3);
            ret = max(ret, product);
 
            product = getNumber(row, column) * getNumber(row + 1, column) * getNumber(row + 2, column) * getNumber(row + 3, column);
            ret = max(ret, product);
 
            product = getNumber(row, column) * getNumber(row + 1, column + 1) * getNumber(row + 2, column + 2) * getNumber(row + 3, column + 3);
            ret = max(ret, product);
 
            product = getNumber(row, column) * getNumber(row + 1, column - 1) * getNumber(row + 2, column - 2) * getNumber(row + 3, column - 3);
            ret = max(ret, product);
        }
    }
 
 
    cout << ret << endl;
 
    system("pause");
    return 0;
}