搜索二维int [] []数组？

Question

How do I search a 2D array for a specific number (1)? I thought the following code did it, but apparently I was looking in a specific spot whenI declared it with [4][4].

    boolean undirectedCircuit (int [][] graph)
{
    //graph = graph1(graph1(null));

    int edgeCounter = 0;

    for (int edge = 0; edge < graph.length; edge++)
    {
        /* SET FOR WHEN 1s are found in array: edgeCounter++;*/
        if(graph[4][4] == '1')
        {
            edgeCounter++;
            System.out.println("edgeCounter found '1' " + edgeCounter + "times");
        }
    }

    if (edgeCounter % 2 == 0)
    {
        System.out.println("This is a circuit!");
        //return true;
    }
    else System.out.println("This is not a circuit!!");
    return false;
    }

public void go ()
{
    graph1 = new int[][] //This line is complained about.
            {
            {0,1,1,1,0},
            {1,0,0,0,1},
            {1,0,0,1,0},
            {1,0,1,0,1},
            {0,1,0,1,0}
            };

    undirectedCircuit(graph1); //This is complained about.
} 

This is part of an assignment from my school, just pointers would be great. Thank you!

Answer 1

You could try something like this where you will iterate through both dimensions of the array and check your current location rather than the 4,4

for (int x = 0; x < graph.length; x++)
        {
            for (int y = 0; y < graph[x].length; y++)
            {
                /* SET FOR WHEN 1s are found in array: edgeCounter++;*/
                if (graph[x][y] == 1)
                {
                    edgeCounter++;
                    System.out.println("edgeCounter found '1' " + edgeCounter + "times");
                }
            }
        }

Answer 2

This line is wrong in two ways:

 if(graph[4][4] == '1')

1. The quotes around '1' make it a char literal. Since your array contains int s, you'll want to drop the quotes and just write 1 .

2. graph[4][4] will always check the same value in the array as you said. Specifically, it will always access the fifth value in the fifth array of your 2d array. Whenever you write numbers in your code, they are constants: the number 4 is never going to change during your program's execution, so you keep using 4 as the index over and over again, accessing the fifth element each time you do so.

In order to access every element in an array, you can loop over it like this:

for (int n = 0; n < array.length; n ++)
{
    array[n]; //access the nth element of the array
}

n in this instance is the same as your edge variable.

However, since you are using a 2d array, these elements are themselves arrays! Therefore, you need another loop:

//array is a 2d array...

for (int n = 0; n < array.length; n ++)
{
    //...so its elements are 1d arrays
    for (int m = 0; m < array[n].length; m ++)
    {
        array[m][n]; //here we have a specific object in our 2d array.
    }
}

We use variables for our indices so they can change in the loop and access different values in the array. Hope this helps!