Pythagorean quadruples: Difference between revisions

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@@ Line 757: / Line 757: @@
 =={{header|Java}}==
+Replace translation with Java coded implementation.
-{{trans|Kotlin}}
-<lang java>public class PythagoreanQuadruple {
+Compute sequence directly.
-    static final int MAX = 2200;
+<lang java>
-    static final int MAX2 = MAX * MAX * 2;
+import java.util.ArrayList;
+import java.util.List;
+public class PythagoreanQuadruples {
     public static void main(String[] args) {
+        long d = 2200;
-        boolean[] found = new boolean[MAX + 1];   // all false by default
+        System.out.printf("Values of d < %d where a, b, and c are non-zero and a^2 + b^2 + c^2 = d^2 has no solutions:%n%s%n", d, getPythagoreanQuadruples(d));
-        boolean[] a2b2  = new boolean[MAX2 + 1];  // ditto
-        int s = 3;
+    }
+    //  See:  https://oeis.org/A094958
-        for (int a = 1; a <= MAX; a++) {
+    private static List<Long> getPythagoreanQuadruples(long max) {
-            int a2 = a * a;
+        List<Long> list = new ArrayList<>();
-            for (int b = a; b <= MAX; b++) a2b2[a2 + b * b] = true;
-        }
+        long n = -1;
+        long m = -1;
-        for (int c = 1; c <= MAX; c++) {
+        while ( true ) {
-            int s1 = s;
+            long nTest = (long) Math.pow(2, n+1);
-            s += 2;
+            long mTest = (long) (5L * Math.pow(2, m+1));
-            int s2 = s;
+            long test = 0;
-            for (int d  = c + 1; d <= MAX; d++) {
+            if ( nTest > mTest ) {
-                if (a2b2[s1]) found[d] = true;
+                test = mTest;
-                s1 += s2;
+                m++;
-                s2 += 2;
+            }
+            else {
+                test = nTest;
+                n++;
+            }
+            if ( test < max ) {
+                list.add(test);
+            }
+            else {
+                break;
             }
         }
+        return list;
-        System.out.printf("The values of d <= %d which can't be represented:\n", MAX);
-        for (int d = 1; d <= MAX; d++) {
-            if (!found[d]) System.out.printf("%d  ", d);
-        }
-        System.out.println();
     }
-}</lang>
+}
+</lang>
 {{out}}
 <pre>
+Values of d < 2200 where a, b, and c are non-zero and a^2 + b^2 + c^2 = d^2 has no solutions:
-The values of d <= 2200 which can't be represented:
-2  4  5  8  10  16  20  32  40  64  80  128  160  256  320  512  640  1024  1280  2048
+[1, 2, 4, 5, 8, 10, 16, 20, 32, 40, 64, 80, 128, 160, 256, 320, 512, 640, 1024, 1280, 2048]
 </pre>