Return the maximum value in subarray

Question

I am trying to return the maximum value in the subarray at index idx and return 0 if index is invalid or if sub array is empty. I have been working on passing this test for a while but I can't seem to do it and I don't know what is wrong with the code.

Answer 1

I'm not sure why you use 2d arrays. I guess that's why you can't get it working.

Here's a solution that works with simple 1d arrays:

static int[] data = new int[] { 1, 4, 2, 3 };

public static int subsetMax(int idx) {
    if(idx >= data.length || idx < 0) {
        return 0;
    }
    int max = 0;
    
    // get the subarray from `idx` til the end of the array
    int[] subarray = Arrays.copyOfRange(data, idx, data.length);

    // for each element in the subarray:
    // check if it is greater than the previous max value
    for(int elem : subarray) {
        max = Math.max(max, elem);
    }
    return max;
}

public static void main(String[] args) {
    System.out.println(subsetMax(-1)); // 0
    System.out.println(subsetMax(0)); // 4
    System.out.println(subsetMax(1)); // 4
    System.out.println(subsetMax(2)); // 3
    System.out.println(subsetMax(3)); // 3
    System.out.println(subsetMax(4)); // 0
}

Answer 2

From the example you provided it seems you are returning array of values.

public static List<Integer> subsetMax(int idx) {
    if(idx >= data.length || idx < 0) {
        return 0;
    }
    int max = 0;
    
    List<Integer>max_values=new ArrayList<>();

    for(int i = 0; i < data.length; i++) {
        max = data[i][0];
       for (int j = 0; j < data[i].length; j++) {
         if(data[i][j]>max) {
                max = data[i][j];
         }
       }
       max_values.add(max);
    }

   return max_values;
}