在20×20的网格中同一直线上四个数的最大乘积是多少？

在以下这个2020的网格中，四个处于同一对角线上的相邻数字用红色标了出来：

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

这四个数字的乘积是：26  63  78  14 = 1788696.

在这个2020网格中，处于任何方向上（上，下，左，右或者对角线）的四个相邻数字的乘积的最大值是多少？

public class Test {
	//从左到右计算最大值
	public static long leftToRight(int arr[][]){
		int max = 0;
		int value = 1;
		for(int i = 0; i < 20; i ++){
			for(int j = 0 ;j < 17 ; j++){
				value = arr[i][j] * arr[i][j+1] * arr[i][j+2] * arr[i][j+3];
				if(value > max) max = value;
			}
			
		}
		return max;
	}
	//从上到下计算最大值
	public static long upToDown(int arr[][]){
		int max = 0;
		int value = 1;
		for(int i = 0; i < 17; i ++){
			for(int j = 0 ;j < 20 ; j++){
				value = arr[i][j] * arr[i+1][j] * arr[i+2][j] * arr[i+3][j];
				if(value > max) max = value;
			}
			
		}
		return max;
		
	}
	//从左上到右下计算最大值
	public static long left_uToRight_d(int arr[][]){
		int max = 0;
		int value = 1;
		for(int i = 0; i < 17; i ++){
			for(int j = 0;j < 17 ; j++){
				value = arr[i][j] * arr[i+1][j+1] * arr[i+2][j+2] * arr[i+3][j+3];
				if(value > max) max = value;
			}
			
		}
		return max;
	}
	//从右上到左下计算最大值
	public static long right_uToLeft_d(int arr[][]){
		int max = 0;
		int value = 1;
		for(int i = 3; i < 20; i ++){
			for(int j = 0 ;j < 17 ; j++){
				value = arr[i][j] * arr[i-1][j+1] * arr[i-2][j+2] * arr[i-3][j+3];
				if(value > max) max = value;
			}
			
		}
		return max;
	}
	public static void main(String[] args) {
		/* 构建20*20整数数组 */
		int arr[][] = {{8,2,22,97,38,15,0,40,0,75,4,5,7,78,52,12,50,77,91,8},  
					  {49,49,99,40,17,81,18,57,60,87,17,40,98,43,69,48,4,56,62,0},  
					  {81,49,31,73,55,79,14,29,93,71,40,67,53,88,30,3,49,13,36,65},  
					  {52,70,95,23,4,60,11,42,69,24,68,56,1,32,56,71,37,2,36,91},  
					  {22,31,16,71,51,67,63,89,41,92,36,54,22,40,40,28,66,33,13,80},  
					  {24,47,32,60,99,3,45,2,44,75,33,53,78,36,84,20,35,17,12,50},  
					  {32,98,81,28,64,23,67,10,26,38,40,67,59,54,70,66,18,38,64,70},  
				  	  {67,26,20,68,02,62,12,20,95,63,94,39,63,8,40,91,66,49,94,21},  
					  {24,55,58,5,66,73,99,26,97,17,78,78,96,83,14,88,34,89,63,72},  
					  {21,36,23,9,75,0,76,44,20,45,35,14,0,61,33,97,34,31,33,95},  
				      {78,17,53,28,22,75,31,67,15,94,3,80,4,62,16,14,9,53,56,92},  
					  {16,39,5,42,96,35,31,47,55,58,88,24,0,17,54,24,36,29,85,57},  
					  {86,56,0,48,35,71,89,7,5,44,44,37,44,60,21,58,51,54,17,58},  
					  {19,80,81,68,5,94,47,69,28,73,92,13,86,52,17,77,4,89,55,40},  
					  {4,52,8,83,97,35,99,16,7,97,57,32,16,26,26,79,33,27,98,66},  
					  {88,36,68,87,57,62,20,72,3,46,33,67,46,55,12,32,63,93,53,69},  
					  {4,42,16,73,38,25,39,11,24,94,72,18,8,46,29,32,40,62,76,36},  
					  {20,69,36,41,72,30,23,88,34,62,99,69,82,67,59,85,74,4,36,16},  
					  {20,73,35,29,78,31,90,1,74,31,49,71,48,86,81,16,23,57,5,54},  
					  {1,70,54,71,83,51,54,69,16,92,33,48,61,43,52,1,89,19,67,48},  
	};  
		System.out.println("max :" + max(leftToRight(arr),upToDown(arr),left_uToRight_d(arr),right_uToLeft_d(arr)));
	}
	private static long max(long a, long b,
			long c, long d) {
		long max = a;
		if(b > max) max = b;
		if(c > max) max = c;
		if(d > max) max = d;
		return max;
	}
	
}