找到二維數組的總和java

Question

我正在研究一個項目，我必須讀取一個文件並將內容輸入到二維數組中。然後我必須對矩陣的每一行，每一列和周長進行求和。除了外圍，我擁有的一切工作至今。我正嘗試爲兩個外側列的頂行，底行和中間創建單獨的for循環。

矩陣文件看起來像這樣：

1 2 3 4 
2 4 6 8 
2 4 6 8 
3 2 3 4 

因此周邊加起來應該42 現在我可以成功添加了第一排和最後一排等於22.然而，當我添加列於總，我得到32

下面是代碼：

import java.util.*; // Scanner class 
import java.io.*; // File class 

public class Lab10 
{ 
    static public void main(String [ ] args) throws Exception 
    {  
    if (args.length != 1) 
    { 
    System.out.println("Error -- usage is: java Lab10 matdataN.txt"); 
    System.exit(0); 
    } 

    //Requirement #1: first int value: # of rows, second int value: # of cols 
    File newFile = new File(args[0]); 
    Scanner in = new Scanner(newFile); 

    int numRows = in.nextInt(); 
    int numCols = in.nextInt(); 

    //Requirement #2: declare two-d array of ints 
    int[][] matrix; 
    matrix = new int[numRows][numCols]; 

    //Requirement #3 & 4: read file one line at a time (nested for loops 
     //and nextInt()) and print 

    for (int i = 0; i < numRows; i++) 
    { 
     for (int j = 0; j < numCols; j++) 
     { 
      matrix[i][j] = in.nextInt(); 
      System.out.print(matrix[i][j]+ " "); 
     } 
    System.out.println(); 
    } 

    //Requirement #5: traverse each row and sum the values and display the sums 
    int rowTotal = 0; 
    for (int i = 0; i < numRows; i++) 
    { 
     rowTotal = 0; 
     for (int j = 0; j < numCols; j++) 
     { 
      rowTotal += matrix[i][j]; 
     } 
    System.out.println("Sum for row = " + rowTotal); 
    } 

    //Requirement #6: traverse each column and sum the values and display the sums 
    int colTotal = 0; 
    for (int i = 0; i < numRows; i++) 
    { 
     colTotal = 0; 
     for (int j = 0; j < numCols; j++) 
     { 
      colTotal += matrix[j][i]; 
     } 
    System.out.println("Sum for col = " + colTotal); 
    } 

    //Requirement #7: traverse the perimeter and sum the values and display the sum 

    //sum bottom row matrix 
    int perTotal = 0; 
    for (int i = (numRows-1); i < numRows; i++) 
    { 
     perTotal = 0; 
     for (int j = 0; j < numCols; j++) 
     { 
      perTotal += matrix[i][j]; 
     } 
    } 

    //sum + top row matrix 
    for (int i = 0; i < numRows - (numRows-1); i++) 
    { 
     for (int j = 0; j < numCols; j++) 
     { 
      perTotal += matrix[i][j]; 
     } 
    System.out.println("Sum of perimeter = " + perTotal); 
    } 

    // sum + first col middle 
    for (int i = 1; i < (numRows-1); i++) 
    { 
     for (int j = 0; j < numCols - (numCols-1); j++) 
     { 
      perTotal += matrix[j][i]; 
     } 
    System.out.println("Sum = " + perTotal); 
    } 

    // sum + last col middle 
    for (int i = 1; i < (numRows-1); i++) 
    { 
     for (int j = (numCols-1); j < numCols; j++) 
     { 
      perTotal += matrix[j][i]; 
     } 
    System.out.println(perTotal); 
    } 

    } 

我會hugeeeeeely感激，如果有人可以幫助我在第一列和最後一列的中間（應該是2 + 2和8 + 8）。或者如果你有一個更好的方式找到周邊。提前致謝！

Answer 1

我建議你這樣說：

int perTotal = 0; 
// top and bottom row 
for (int c = 0; c < numCols; c++) 
    perTotal += matrix[0][c] + matrix[numRows-1][c]; 
// left and right column 
for (int r = 1; r < numRows-1; r++) 
    perTotal += matrix[r][0] + matrix[r][numCols-1]; 

// output 
System.out.println("Perimeter=" + perTotal); 

Answer 2

 //Requirement #7: traverse the perimeter and sum the values and display the sum 

     int perTotal = 0; 

     // First line 
     for (int j = 0; j < numCols; j++) 
     { 
      perTotal += matrix[0][j]; 
     } 

     // If there is only one line, then it is done. 
     if (numRows > 1) 
     { 
      // Last line 
      for (int j = 0; j < numCols; j++) 
      { 
       perTotal += matrix[numRows-1][j]; 
      } 

      // Other lines 
      for (int i = 1; i < numRows -1); i++) 
      { 
       perTotal += matrix[i][0] + matrix[i][numcols -1]; 
      } 
     } 

    //Perimeter 
    System.out.println("Perimter="+perTotal); 

Answer 3

這裏是你的方法：

public static int perimeter(int[][] array) { 
    int perimter = 0; 
    for (int i = 0; i < array[0].length; i++) { 
     perimter += array[0][i] + array[array.length - 1][i]; 
    } 
    for (int r = 1; r < array.length - 1; r++) { 
     perimter += array[r][0] + array[r][array[0].length - 1]; 
    } 
    return perimter; 
} 

這裏是你提供的陣列測試：

public static void main（String [] args）{ System.out.println（perimeter（new int [] [] {{1,2,3,2}，{2,4,4,2}，{3,6,6,3}，{4,8 ，8，4}}））; }

輸出：42

Answer 4

感謝大家這麼多！這樣做更簡單。 FYI：我落得這樣做

int perTotal = 0; 
    for (int i = 0; i < numCols; i++) 
    { 
     perTotal += matrix[0][i] + matrix[numRows-1][i]; 
    } 
    for (int j = 1; j < numRows-1; j++) 
    { 
     perTotal += matrix[j][0] + matrix[j][numCols-1]; 
    } 
    System.out.println("Perimeter = " + perTotal); 

Answer 5

有一個la4j（線性代數爲Java）庫處理這個任務在0.4.0版本（在GitHub上目前可供選擇：https://github.com/vkostyukov/la4j，將在Maven的這個夏天avaliable）。所以，這裏是簡單的例子：

Matrix a = new Basic2DMatrix(...); // creates a real matrix 

// calculates the sum of '1' row 
double d1 = a.foldRow(1, Matrices.asSumAccumulator(0)); 
// calculates the sum of '2' 
double d2 = a.foldColumn(2, Matrices.asSumAccumulator(0)); 

// the helper class that fetches border elements of matrix 
class PerimeterFetcher implements MatrixFunction { 

    private int rows; 
    private int columns; 

    public PerimeterFectcher(int rows, int columns) { 
    this.rows = rows; 
    this.columns = columns; 
    }  

    @Override 
    public double evaluate(int i, int j, double value) { 
    return i == 0 ? value : j == 0 ? value : (i + 1) == rows ? value 
      : (j + 1) == columns ? value : 0; 
    } 
} 

// calculates the perimeter of matrix 
double p = a.fold(Matrices.asSumFunctionAccumulator(0, 
        new PerimeterFetcher(a.rows(), a.columns())));  

UPD：la4j的下一個版本（0.4.5）支持sum()法向量和矩陣：

Matrix a = new Basic2DMatrix(...); 
double s = a.sum(); // wrapper around a.fold(...); 

Answer 6

只是這樣做：

 for (int i = 0; i < ROWS; i++){ 
      for (int j = 0; j < COLUMNS; j++){ 
      sum = sum + myArray[i][j]; 
     } 
    } 

    System.out.print(sum); 

這應該給你的總和。

Answer 7

嘗試以下操作：

import java.util.Scanner; 
public class TwoDarray { 

public static void main(String[] args) 
{ 
    Scanner scn=new Scanner(System.in); 

    System.out.print("Enter the first Rows of Array :"); //Input first Rows and Columns 
    int row1 = scn.nextInt(); 
    System.out.print("Enter the first columns of Array:"); 
    int col1 = scn.nextInt(); 
    System.out.print("Enter the second Rows of Array :"); //Input second rows and column 
    int row2 = scn.nextInt(); 
    System.out.print("Enter the second columns of Array:"); 
    int col2 = scn.nextInt(); 

    int arr1[][] = new int[row1][col1];      // Input the elements in first row and column 

      System.out.println("Enter the elements in First row and column"); 
       for(int i=0;i<row1;i++) 
       { 
        for(int j=0;j<col1;j++) 
        { 
         arr1[i][j]=scn.nextInt(); 
        } 
       } 

    int arr2[][] = new int[row2][col2];      // Input the elements in second row and column 

     System.out.println("Enter the elements in second row and column"); 
      for(int i=0;i<row2;i++) 
      { 
       for(int j=0;j<col2;j++) 
       { 
        arr2[i][j]=scn.nextInt(); 
       } 

      } 

    System.out.println("Output of first row and column is ");  //output of first row and column 
     for(int i=0;i<row1;i++) 
     { 
      for(int j=0;j<col1;j++) 
      { 
       System.out.print(arr1[i][j]+" "); 
      } System.out.println(); 
     } 

       System.out.println("output of secound row and column");   //out put of second row and column 
        for(int i=0;i<row2;i++) 
        { 
         for(int j=0;j<col2;j++) 
         { 
          System.out.print(arr2[i][j]+" "); 
         }  System.out.println(); 
        } 


                 //sum of first and second row and column 

        int sum[][] = new int[row1][col1]; 
         for(int i=0;i<row1;i++) 
         { 
          for(int j=0;j<col1;j++) 
          { 
           sum[i][j]=arr1[i][j]+arr2[i][j]; 
          } 
         } 

         System.out.println("sum of two matrix output");   //sum of two matrix output 
          for(int i=0;i<row1;i++) 
          { 
           for(int j=0;j<col1;j++) 
           { 
            System.out.print(sum[i][j]+" "); 
           }  System.out.println(); 
          } 

} 


}