项目欧拉＃11 java。没有得到正确的答案 [英] Project Euler #11 java. Not getting the right answer

问题描述

我对Project Euler上的问题11 有些问题。
我设法得到答案，但这不是正确的答案。我得到 51267216 。
这是通过 largestVert 方法找到的。我认为问题出在 largestDiaglonal 方法中，但我不太确定。有人可以检查我的算法是否正确吗？

I have some problems with Problem 11 on Project Euler. I manage to get an answer, but it's not the right one. I'm getting 51267216. This is found by the greatestVert method. I think the problem is located in the greatestDiaglonal method, but I'm not quite sure. Can somebody check if my algorithm is correct?

任务是找出任意方向上四个相邻数字的最大乘积（上，下，左，右，或对角线）在20x20网格中。

The task is to find out what the greatest product of four adjacent numbers in any direction (up, down, left, right, or diagonally) is in the 20x20 grid.

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);
}
}

推荐答案

你省略扫描对角线的一个方向：

You are omitting to scan one direction of diagonals:

for(int i = 0; i>=16; i++) {

根本不运行。你的意思是 i< = 16 那里。

doesn't run at all. You meant i <= 16 there.

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