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POOvercoming heap overflow issues
 

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  1. POOvercoming heap overflow issues
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    <p>I tried to solve problems from Project Euler. I know my method would work logically (it returns answers to the small scale problem almost instantly). However, it scales horribly. I already attempted changing the .ini file, but to no avail.</p> <p>Here's my code:</p> <pre><code>public class Number28 { static int SIZE = 101; //this should be an odd number, i accidentally posted 100 /** * @param args */ public static void main(String[] args) { double start = System.currentTimeMillis(); long spiral[][]= spiral(SIZE); long sum = 0; for(int i = 0; i &lt; SIZE; i++) { sum += spiral[i][i]; sum += spiral[i][SIZE - 1 - i]; } System.out.println(sum - 1); double time = System.currentTimeMillis() - start; System.out.println(time); } public static long[][] spiral(int size){ long spiral[][]= new long[size][size]; if(size == 1){ spiral[0][0] = 1; return spiral; } else{ long subspiral[][]= new long[size - 2][size - 2]; subspiral = spiral(size - 2); for(int r = 0; r &lt; size - 2; r++){ for(int c = 0; c &lt; size - 2; c++){ spiral[r + 1][c + 1] = subspiral[r][c]; } } long counter = subspiral[0][size - 3]; for(int r = 1; r &lt; size ; r++){ counter++; spiral[r][size - 1] = counter; } for(int c = size - 2; c &gt;= 0; c--){ counter++; spiral[size - 1][c] = counter; } for(int r = size - 2 ; r &gt;= 0 ; r--){ counter++; spiral[r][0] = counter; } for(int c = 1; c &lt; size ; c++){ counter++; spiral[0][c] = counter; } return spiral; } } } </code></pre> <p>Here's the edited code, worked like a gem:</p> <pre><code>public class Number28 { static int SIZE = 1001; static long spiral[][]= new long[SIZE][SIZE]; /** * @param args */ public static void main(String[] args) { double start = System.currentTimeMillis(); long spiral[][]= spiral(SIZE); long sum = 0; for(int i = 0; i &lt; SIZE; i++) { sum += spiral[i][i]; sum += spiral[i][SIZE - 1 - i]; } System.out.println(sum - 1); double time = System.currentTimeMillis() - start; System.out.println(time); } public static long[][] spiral(int size){ if(size == 1){ spiral[SIZE / 2][SIZE / 2] = 1; return spiral; } else{ long subspiral[][]= spiral(size - 2); int edge = (SIZE - size) / 2; long counter = subspiral[edge + 1][edge + size - 2]; for(int r = 1; r &lt; size ; r++){ counter++; spiral[edge + r][edge + size - 1] = counter; } for(int c = size - 2; c &gt;= 0; c--){ counter++; spiral[edge + size - 1][edge + c] = counter; } for(int r = size - 2 ; r &gt;= 0 ; r--){ counter++; spiral[edge + r][edge] = counter; } for(int c = 1; c &lt; size ; c++){ counter++; spiral[edge][edge + c] = counter; } return spiral; } } } </code></pre>
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    1. COWhat is the problem you are trying to solve? Can you quote #28 here?
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    2. COYou've got an unneeded memory allocation at: long subspiral[][]= new long[size - 2][size - 2]; Your next line should just be: long subspiral[][] = spiral(size - 2);
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      1. USSteven
    3. COProblem 28 is here: http://projecteuler.net/index.php?section=problems&id=28 The final goal is to find the sum of the cross on a 1001 by 1001 spiral, but this heap overflowed at 100. I'm going to try everyone's advice and report back.
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