项目Euler #11

Question

我最近开始了这些项目，以测试我的Java技能。我解决了问题11，把前面的问题都做对了。我的代码有问题。返回的答案似乎是正确的，但当我在官方网站上检查时却并非如此:问题出在Project Euler #11。

这是我的代码。我已经注释掉了几行调试代码。忽略它们就好。

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");
}

如果放入一个类中，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

Answer 1

两次检查的都是相同的对角线。在网格中(在纸上)绘制您正在检查的线条，以便于查看。

将它们中的一个更改为从X添加和从Y减去(或相反)。

Answer 2

以下是一些小贴士：

• 你不需要这样：

C= source.charAt(x)；c1 = source.charAt(x + 1)；s=新字符串(c，0，2)；

你可以直接写

s= source.charAt(x) +""+ source.charAt(x+1)；

或者更好的使用

S= source.substring(x，x+2)；

• 检查更简单的data

• 上的对角线如果您确实不需要写入

• gird.length

• 20

，请不要交换内部外部

Answer 3

我认为你的代码的问题在于你试图使用字符串。尝试使用3d数组重写它。我的解决方案大约有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    }