歐拉項目＃11

Question

我最近開始這些項目來測試我的Java技能。我遇到了問題11，所有以前的問題都對了。我的代碼有問題。返回的答案似乎是正確的，但不是當我在官方網站上檢查它時： 問題在於Project Euler #11。

這是我的代碼。我有幾條註釋掉調試線。只要忽略它們。

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"); 
} 

如果放在課堂上，這是可編譯的。我只是不知道爲什麼它是錯的。

輸出：

48477312 - Horizontal Answer 
51267216 - Vertical Answer 
32719995 - Diagonal "\" Answer 
40304286 - Diagonal "/" Answer 

51267216 - Final Answer 

Answer 1

要檢查同一斜線兩次。在網格中繪製你正在檢查的線條（在紙上），以便輕鬆查看。

更改其中一個從X添加並從Y減去（或相反方向）。

Answer 2

一些提示：

• 你不需要這樣的：

  c[0] = source.charAt(x); 
  c[1] = source.charAt(x + 1); 
  s = new String(c, 0, 2); 
  

  ，你可以只寫

  S = source.charAt（X）+ 「」 + source.charAt （X + 1）;

  或甚至更好使用

  S = source.substring（X，X + 2）;

• 檢查簡單的數據

  對角線

• 不要交換內外部的，如果你真的不需要

• 寫gird.length而不是20

Answer 3

我認爲你的代碼有什麼問題是你正在嘗試使用字符串。嘗試使用3D數組重新編寫它。我的解決方案有大約14行代碼。

公共類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 } 

Answer 4

你/對角線的計算是錯誤我想.. 我已經在Java解決了它：

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]); 
     } 
    } 

Answer 5

您應該使用整數數組，有太多在你的實現中輸入castings，使用數組索引也容易得多。

我使用一維數組編寫了一個簡單的代碼（在JavaScript tho中），它具有O（n）複雜性。

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); 

在編寫代碼時，您應該始終考慮到執行所需的複雜性和時間。通過少量代碼優化，您可以將解決方案改進幾秒鐘。

乾杯。