给定两个2D数组，将它们添加到第三个2D数组中

Question

I am going through everything that I learned over the course of this quarter and re-studying the topics that I feel I didn't truly grasp. One of them was the concept of adding a third 2D array that stores the information for a previous 2D array.

The specific statement of what I should know by the end of this quarter was:

"Given two 2D arrays, add them into a third 2D array"

Here are my attempts to do this:

public static void main (String[] args){
int [] [] arrayOneTwoD= {{5,4,3,2,1},{1,2,3,4,5}};
        int [] [] arrayTwoTwoD={{9,8,7,6,5},{5,6,7,8,9}};
        int [][] thirdArray= new int [4][4];

thirdArray(arrayOneTwoD,arrayTwoTwoD,thirdArray);
}

public static void thirdArray (int [][] arrayOneTwoD, int [][] arrayTwoTwoD, int [] []thirdArray){

        for(int i = 0; i < 3; ++i) {
            for(int j = 0; j < 3; ++j) {
                thirdArray[i][j] = arrayOneTwoD[i][j] + arrayTwoTwoD[i][j]; 
            }
        }
    }

I searched this topic on stack overflow a number of times but nothing comes up for printing into a third 2D array only from one single 2D array into another.

What am I doing wrong?

Answer 1

you should do something like this:

public static void main (String[] args){
    int [][] arrayOneTwoD= {{5,4,3,2,1},{1,2,3,4,5}};
    int [][] arrayTwoTwoD={{9,8,7,6,5},{5,6,7,8,9}};
    int [][] thirdArray = thirdArray(arrayOneTwoD,arrayTwoTwoD);
}

public static int[][] thirdArray(int[][] arrayOneTwoD, int[][] arrayTwoTwoD){
    // assuming both arrays have the same dimensions
    int[][] thirdArray = new int[arrayOneTwoD.length][arrayOneTwoD[0].length];
    for(int i = 0; i < arrayOneTwoD.length; ++i) {
        for(int j = 0; j < arrayOneTwoD[0].length; ++j) {
            thirdArray[i][j] = arrayOneTwoD[i][j] + arrayTwoTwoD[i][j]; 
        }
    }
    return thirdArray;
}

You'll want to figure out the dimensions of the arrays you're adding instead of hard-coding a value when you initialize the 3rd 2D array. You'll also need these dimensions when you iterate in your for loop. If the two 2D arrays you're adding are different dimensions, the answer becomes a little more complicated.