我对 Project Euler的问题 11有一些问题。我设法得到一个答案，但它不是正确的。我得到51267216。这是通过greatestVert方法找到的。我认为问题出在greatestDiaglonal方法上，但我不太确定。有人可以检查我的算法是否正确吗？
任务是找出任何方向（上、下、左、右或对角线）上四个相邻数字的最大乘积在 20x20 网格中。
package euler;
public class Problem11 {
int num1, num2, num3, num4;
int highestNum1, highestNum2, highestNum3, highestNum4;
private int sum = 0;
String[] l = {
"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"
};
int greatestSide() {
for(int i = 0;i<=19;i++) {
for(int n = 0;n<=l[i].length()-12;n+=3) {
num1 = Integer.parseInt(l[i].substring(0+n,3+n).trim());
num2 = Integer.parseInt(l[i].substring(3+n,6+n).trim());
num3 = Integer.parseInt(l[i].substring(6+n,9+n).trim());
num4 = Integer.parseInt(l[i].substring(9+n,12+n).trim());
if(num1*num2*num3*num4 > sum) {
sum = num1*num2*num3*num4;
highestNum1 = num1;
highestNum2 = num2;
highestNum3 = num3;
highestNum4 = num4;
}
}
}
return sum;
}
int greatestVert() {
for(int i = 0; i<=16; i++) {
for(int n = 0; n<=l[i].length()-3; n+=3) {
num1 = Integer.parseInt(l[i].substring(0+n,3+n).trim());
num2 = Integer.parseInt(l[i+1].substring(0+n,3+n).trim());
num3 = Integer.parseInt(l[i+2].substring(0+n,3+n).trim());
num4 = Integer.parseInt(l[i+3].substring(0+n,3+n).trim());
if(num1*num2*num3*num4 > sum) {
sum = num1*num2*num3*num4;
highestNum1 = num1;
highestNum2 = num2;
highestNum3 = num3;
highestNum4 = num4;
}
}
}
return sum;
}
int greatestDiagonal() {
for(int i = 19; i>=3; i--) {
for(int n = 0; n<=l[i].length()-12; n+=3) {
num4 = Integer.parseInt(l[i].substring(9+n,12+n).trim());
num3 = Integer.parseInt(l[i-1].substring(6+n,9+n).trim());
num2 = Integer.parseInt(l[i-2].substring(3+n,6+n).trim());
num1 = Integer.parseInt(l[i-3].substring(0+n,3+n).trim());
if(num1*num2*num3*num4 > sum) {
sum = num1*num2*num3*num4;
highestNum1 = num1;
highestNum2 = num2;
highestNum3 = num3;
highestNum4 = num4;
}
}
}
for(int i = 0; i>=16; i++) {
for(int n = 0; n<=l[i].length()-12; n+=3) {
num4 = Integer.parseInt(l[i].substring(9+n,12+n).trim());
num3 = Integer.parseInt(l[i+1].substring(6+n,9+n).trim());
num2 = Integer.parseInt(l[i+2].substring(3+n,6+n).trim());
num1 = Integer.parseInt(l[i+3].substring(0+n,3+n).trim());
if(num1*num2*num3*num4 > sum) {
sum = num1*num2*num3*num4;
highestNum1 = num1;
highestNum2 = num2;
highestNum3 = num3;
highestNum4 = num4;
}
}
}
return sum;
}
public static void main(String[] args) {
Problem11 prog = new Problem11();
prog.greatestSide();
prog.greatestVert();
prog.greatestDiagonal();
System.out.println(prog.sum);
System.out.println(prog.highestNum1);
System.out.println(prog.highestNum2);
System.out.println(prog.highestNum3);
System.out.println(prog.highestNum4);
}
}