debug problem in the checking, old wizards cult riddle

Question

I'm trying to solve this riddle in java, about an old man who lives because his cult who gives the old man some of their life, this specific code should work to the rules which are given but one of the checks in the testing is an error.

public class hello {
    /** set true to enable debug */
    static boolean debug = true;

    static long old(int n, int m, int k, int newp) {
            int max;
            int min;
        boolean moreRows;

    if (m > n) {
        min = n;
        max = m;
        moreRows = true;
    } else {
        min = m;
        moreRows = false;
        max = n;
    }
    int sum = 0;
    int[][] ar2 = new int[(int)m][(int)n];
    // square part
    for (int i = 0; i < min; i++) {
        for (int j = 0; j < i; j++) {
           int t = i ^ j;
            ar2[i][j] = t - (t >= k ? k : 0);;
            sum += 2 * t- (t >= k ? k : 0);;
        }
    }
    for (int i = min; i < max; i++) {
        for (int j = 0; j < min; j++) {
            int t = i ^ j;
            sum += t;
            if (moreRows) {
                ar2[i][j] = t - (t >= k ? k : 0);
            } else {
                ar2[j][i] = t;
            }
        }
    }
        //retrun time
            while(newp<sum && newp>0) {
                sum=sum-newp;//wrap it up
            }
            return sum;
    }
  }

here is the assert equals test which contains multiple examples:

import org.junit.AfterClass;
import org.junit.BeforeClass;
import org.junit.Test;

import static org.junit.Assert.assertEquals;
import static org.junit.Assert.fail;

public class HelloTest {

    @Test
    public void example() {
        assertEquals(5, Hello.olde(8, 5, 1, 100));
        assertEquals(224, Hello.old(8, 8, 0, 100007));
        assertEquals(11925, Hello.old(25, 31, 0, 100007));
        assertEquals(4323, Hello.old(5, 45, 3, 1000007));
        assertEquals(1586,Hello.old(31, 39, 7, 2345));
        assertEquals(808451, Hello.old(545, 435, 342, 1000007));
        // You need to run this test very quickly before attempting the actual tests :)
        assertEquals(5456283, Hello.old(28827050410L, 35165045587L, 7109602, 13719506));
    }

}

i get the following errors which looks like a long to int-

./src/test/java/HelloTest.java:19: error: incompatible types: possible lossy conversion from long to int
        assertEquals(5456283, hello.old(28827050410L, 35165045587L, 7109602, 13719506));
                                                ^
Note: Some messages have been simplified; recompile with -Xdiags:verbose to get full output
1 error

some more errors from harder examples-

        assertEquals(5456283, Hello.old(28827050410L, 35165045587L, 7109602, 13719506));
                                                ^
./src/test/java/HelloTest.java:39: error: incompatible types: possible lossy conversion from long to int
            long expected = Hello.old(m, n, l, t), actual = Hello.old(m, n, l, t);

debug some errors in one of the assert equals and harder examples, I can't really think what can be changed, I'm sure it's something small so help would be appreciated-Note: t will never be bigger than 2^32 - 1(from the instructions of the question) thanks

Answer 1

According to my knowledge, you cant take more than int in the size of an array but if you don't want to change your long everywhere, you can probably add cast.

long m = 434;
    int[] obj = new int[(int) m];

Attempting to access beyond the maximum value allowed through an iterator associated with the array would likely result in one of OutOfMemoryException, IndexOutOfBoundsException or a NoSuchElementException depending on implementation.

This is a very impractical use of memory. If one was to want such a data structure, one should investigate less RAM intensive approaches such as databases, sparse arrays, and the like.

Answer 2

1. The last test will NOT run on a single machine as long values cannot be used as array length and indexes. This has already been explained in the answer/comments to your previous question.

However, it can be deducted from the task that you do not need to store intermediate data in the array at all, you should just calculate the total.

And even if array is not used it is very likely to take a long time to complete the nested loop with 28_827_050_410 * 35_165_045_587L / 2 iterations. If you had a processor with performance of 100 GFlop/s it should be able to count that in over 160 years.

2. The calculation of t and sum is incorrect.

It should be:

int t = i ^ j;
if (t >= k) {
    t -= k;
}
sum += 2 * t; // or sum += t in the second part.

3. The last loop seems to be replaceable with simple return sum % newp;

---

Update:

Function old may be refactored as follows (to get rid of the arrays), though it is still a "naive" solution which would not pass the last test.

static int old(int n, int m, int k, int newp) {
    int max;
    int min;

    if (m > n) {
        min = n;
        max = m;
    } else {
        min = m;
        max = n;
    }
    int sum = 0;
    // square part
    for (int i = 0; i < min; i++) {
        for (int j = 0; j < i; j++) {
            int t = i ^ j;
            if (t >= k) {
                t -= k;
                sum += 2 * t;
            }            
        }
    }
    for (int i = min; i < max; i++) {
        for (int j = 0; j < min; j++) {
            int t = i ^ j;
            if (t >= k) {
                t -= k;
                sum += t;
            }
        }
    }
    return sum % newp;
}

Output for the 6 tests:

OK! 5
OK! 224
OK! 11925
OK! 4323
OK! 1586
OK! 808451