我最近开始使用Java来测试我的技能。我遇到问题11，让所有以前的问题都正确。我的代码有问题。返回的答案似乎是正确的，但是当我在官方网站上查看它时，它不是： 问题发生在Project Euler #11。
这是我的代码。我有几个注释掉的调试行。只是忽略它们。
static String source = "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";
// static String source = "02 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 03 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 04 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 01 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00";
static int[] numList = new int[400];
static int answer;
public static void main(String args[]){
int counter = 1;
int numListCounter = 0;
//convert source to array
for(int x = 0; x < source.length(); x++){
char[] c = new char[2];
String s;
if(counter == 1){
c[0] = source.charAt(x);
c[1] = source.charAt(x+1);
s = new String(c,0,2);
numList[numListCounter] = Integer.parseInt(s);
}
if(counter == 3){
numListCounter++;
counter = 0;
}
counter++;
}
//convert array to grid
int[][] grid = new int[20][20];
int c = 0;
for(int x = 0; x < 20; x++){
for(int y = 0; y < 20; y++){
grid[y][x] = numList[c];
c++;
}
}
//Prints the array. used for testing.
/*
for(int y = 0; y < 20; y++){
for(int x = 0; x < 16; x++){
System.out.print(grid[x][y] + "\t");
}
System.out.println();
}
*/
//check horizontal
int hAnswer = 0;
for(int y = 0; y < 20; y++){
for(int x = 0; x < 16; x++){
if(grid[x][y]*grid[x+1][y]*grid[x+2][y]*grid[x+3][y] > hAnswer){
hAnswer = grid[x][y]*grid[x+1][y]*grid[x+2][y]*grid[x+3][y];
// System.out.println(x + " , " + y);
// System.out.println(answer);
}
}
}
if(hAnswer > answer){
answer = hAnswer;
}
System.out.println(hAnswer + " - Horizontal Answer");
//check vertical
int vAnswer = 0;
for(int x = 0; x < 20; x++){
for(int y = 0; y < 16; y++){
if(grid[x][y]*grid[x][y+1]*grid[x][y+2]*grid[x][y+3] > vAnswer){
vAnswer = grid[x][y]*grid[x][y+1]*grid[x][y+2]*grid[x][y+3];
// System.out.println(x + " , " + y);
// System.out.println(answer);
}
}
}
if(vAnswer > answer){
answer = vAnswer;
}
System.out.println(vAnswer + " - Vertical Answer");
//check diagonal \
int d1answer = 0;
for(int y = 0; y < 16; y++){
for(int x = 0; x < 16; x++){
if(grid[x][y]*grid[x+1][y+1]*grid[x+2][y+2]*grid[x+3][y+3] > d1answer){
d1answer = grid[x][y]*grid[x+1][y+1]*grid[x+2][y+2]*grid[x+3][y+3];
// System.out.println(x + " , " + y);
// System.out.println(answer);
}
}
}
if(d1answer > answer){
answer = d1answer;
}
System.out.println(d1answer + " - Diagonal \"\\\" Answer");
//check diagonal /
int d2answer = 0;
for(int y = 3; y < 20; y++){
for(int x = 3; x < 20; x++){
if(grid[x][y]*grid[x-1][y-1]*grid[x-2][y-2]*grid[x-3][y-3] > d2answer){
d2answer = grid[x][y]*grid[x-1][y-1]*grid[x-2][y-2]*grid[x-3][y-3];
// System.out.println(x + " , " + y);
// System.out.println(answer);
}
}
}
if(d2answer > answer){
answer = d2answer;
}
System.out.println(d2answer + " - Diagonal \"/\" Answer");
System.out.println();
System.out.println(answer + " - Final Answer");
}
如果放入类中，这是可编译的。我只是不知道为什么这是错的。
输出：
48477312 - Horizontal Answer
51267216 - Vertical Answer
32719995 - Diagonal "\" Answer
40304286 - Diagonal "/" Answer
51267216 - Final Answer
答案 0 :(得分：5)
您正在检查相同的对角线。在网格中绘制您正在检查的线条（在纸上），以便轻松查看。
将其中一个更改为从X添加并从Y减去（或反过来）。
答案 1 :(得分：1)
一些提示：
你不需要这个：
c[0] = source.charAt(x);
c[1] = source.charAt(x + 1);
s = new String(c, 0, 2);
你可以写
s = source.charAt（x）+“”+ source.charAt（x + 1）;
甚至更好地使用
s = source.substring（x，x + 2）;
检查更简单数据上的对角线
如果您确实不需要
写gird.length而不是20
答案 2 :(得分：1)
我认为你的代码出了什么问题就是你试图使用字符串。尝试使用3d数组重写它。我的解决方案有大约14行代码。
公共类P11 {
int max, digits;
int[][] grid = {
P11() {
max = 0;
digits = 4;
}
public void run() {
for (int i=0; i<grid.length-digits+1; i++)
for (int j=0; j<grid.length-digits+1; j++) {
//iterate through the grid }
System.out.println(max);
}
private int getMaxProduct(int xIndex, int yIndex) {
int p1=1, p2=1, p3=1, p4=1;
for (int i=0; i<digits; i++) {
///find all the products }
return //maximum product }
答案 3 :(得分：0)
您的/对角线计算错误我猜... 我在java中解决了它：
for (i = 0; i < 17; i++) {
for (j = 3; j < 20; j++) {
product.add(twoDArray[i][j] * twoDArray[i + 1][j - 1] * twoDArray[i + 2][j - 2] * twoDArray[i + 3][j - 3]);
}
}
答案 4 :(得分：0)
你应该使用整数数组，你的实现中有太多的类型转换，使用数组索引也更容易。
我使用一维数组编写了一个简单的代码（在javascript中），具有O（n）复杂度。
var input = [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];
var start = Date.now();
var max = 0;
var row = 0;
var rowIndex = 0;
for (var i = 0; i < input.length - 3; i++) {
var tmpProd;
if(rowIndex < 17) {
tmpProd = input[i] * input[i+1] * input[i+2] * input[i+3];
if(tmpProd > max) max = tmpProd;
}
if(row < 17) {
tmpProd = input[i] * input[i+20] * input[i+40] * input[i+60];
if(tmpProd > max) max = tmpProd;
}
if(rowIndex < 17 && row < 17) {
tmpProd = input[i] * input[i+21] * input[i+42] * input[i+63];
if(tmpProd > max) max = tmpProd;
}
if(rowIndex > 2 && row < 17) {
tmpProd = input[i] * input[i+19] * input[i+38] * input[i+57];
if(tmpProd > max) max = tmpProd;
}
if(rowIndex < 17 && row > 2) {
tmpProd = input[i] * input[i-19] * input[i-38] * input[i-57];
if(tmpProd > max) max = tmpProd;
}
if(rowIndex == 19) {
rowIndex = 0;
row++;
} else {
rowIndex++;
}
}
console.log('time: ', Date.now() - start);
console.log('max: ', max);
在编写代码时，您应始终牢记其执行所需的复杂性和时间。只需很少的代码优化，您就可以在几秒钟内完善解决方案。
干杯。