Java扫描仪/阵列金字塔

Question

So I'm trying to make a pyramid of added values. Ex. Line 1 has (5), Line 2 has (6,7) Line 3 has (12,10,7). The goal is to add the highest value of the first line, with the highest connecting child value of the next line. So in this case, you would add 5+7+10, giving you a result of 22. The reason why you can't use the 12 in line 3 is because you have to use a child of the number above (Each parent has 2 children).

My approach is to use Scanner to load int values into an array line-by-line, and somehow index the position of the previous line's highest child value to add it to a running total. Here's the code I have so far...

//in the data file...

5

6 7

12 10 7

//that's all.

    public static void main(String[] args) {
    Scanner scanner = null;
    try {
        scanner = new Scanner(new File("/users/joe/desktop/data.txt"));
    } catch (FileNotFoundException e) {
        System.out.println("File not found.");
        e.printStackTrace();

    } //reads the file

    int[] a = new int[100]; //establishes new array with a max size of 100
    int i = 0; //placeholder for array position
    int result = 0;
    int total = 0;

    while(scanner.hasNextLine()){ //loops through line
        a[i++] = scanner.nextInt(); //adds int to array
        if(i == 0){ //does this belong here?
            result = a[0];
        }
        else{
            if(a[i-1] >= a[i+1]){
                result = a[i-1];
            }
            else if(a[i-1] <= a[i+1]){
                result = a[i+1];
            }
        }
    }
    total =  total + result;
    scanner.close();

    System.out.print(Arrays.toString(a));
    System.out.println("\n" + total);


    }
    }

Currently, this will print out: [5,6,7,12,10,7,0,0,0,0,0,...up to 100 positions]

5

How can I get the Scanner to read one line, load it into an array, loop that, and save the highest child value from the next line's array?

Answer 1

When I execute that code, I get a NoSuchElementException after reading in all the numbers. This occurs because you are always checking for the next line of the file, but reading in the next integer.

There are so many logic flaws in the code that its hard to comment on them all. Here's a few that you could work on:

You only add total + result ONCE, outside of your loop. You should move that inside a loop so total is calculated properly

You calculate result incorrectly. At the very least, you should have a variable indicating the position of the highest number on the last row. You also are comparing i -1 with i+1... this won't work when you get down to the last row, as you'll be comparing items to either side of i rather than items below i.

I'd recommend reading the variables into a triangular 2D array. You can do this by creating another scanner for each line; reading each line into the new scanner; and polling for nextInt(). This then lets you compare arr[row][pos] and arr[row][pos+1] which will be the children of arr[row-1][pos].

Once you can read the file into a 2D array and print int out from the array to look just like the file contents, and if you're still having trouble, come back and I can give you some more help.