Fixed #13, added tests for multiply using FFT and using loops with st…

…ring input, does appear to have exposed a bug
DD2480-group11 · Feb 23, 2022 · f8f6e97 · f8f6e97
1 parent cb84fe5
commit f8f6e97
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Showing 2 changed files with 57 additions and 3 deletions.
diff --git a/src/com/jwetherell/algorithms/mathematics/Multiplication.java b/src/com/jwetherell/algorithms/mathematics/Multiplication.java
@@ -7,6 +7,19 @@
 
 public class Multiplication {
 
+    static boolean[] reachedBranch = new boolean[200];
+    private static void BRANCH(int index) {
+        if (!reachedBranch[index]) {
+            reachedBranch[index] = true;
+            System.out.println("--------------");
+            for (int i = 0; i < reachedBranch.length; i++) {
+                if (reachedBranch[i]) {
+                    System.out.println("REACHED BRANCH #" + i);
+                }
+            }
+        }
+    }
+
     public static final long multiplication(int a, int b) {
         long result = ((long) a) * ((long) b);
         return result;
@@ -131,19 +144,27 @@ public static String multiplyUsingLoopWithStringInput(String a, String b) {
         boolean aIsNegative = false;
         ArrayList<Integer> first = new ArrayList<Integer>();
         for (char n : a.toCharArray()){
+            BRANCH(1+100);
             if (n=='-') {
+                BRANCH(2+100);
                 aIsNegative = true;
                 continue;
+            }else{
+                BRANCH(3+100);
             }
             first.add(n-'0');
         }
 
         boolean bIsNegative = false;
         ArrayList<Integer> second = new ArrayList<Integer>();
         for (char n : b.toCharArray()){
+            BRANCH(4+100);
             if (n=='-') {
+                BRANCH(5+100);
                 bIsNegative = true;
                 continue;
+            }else{
+                BRANCH(6+100);
             }
             second.add(n-'0');
         }
@@ -153,8 +174,10 @@ public static String multiplyUsingLoopWithStringInput(String a, String b) {
 
         ArrayList<Integer> res = new ArrayList<Integer>(Collections.nCopies(first.size()+second.size(), 0));
         for (i=0;i<=lim1;i++) {
+            BRANCH(7+100);
             k=i;
             for (j=0;j<=lim2;j++) {
+                BRANCH(8+100);
                 int f = first.get(i);
                 int s = second.get(j);
                 mul=f*s;
@@ -165,26 +188,43 @@ public static String multiplyUsingLoopWithStringInput(String a, String b) {
         }
 
         for (i=(lim1+lim2)+1;i>=0;i--) {
+            BRANCH(9+100);
             if (flag==1){
+                BRANCH(10+100);
                 res.set(i,res.get(i)+carry);
                 flag=0;
+            }else{
+                BRANCH(11+100);
             }
 
             if (res.get(i)>=10 && i!=0) {
+                BRANCH(12+100);
                 rem=res.get(i)%10;
                 carry=res.get(i)/10;
                 res.set(i,rem);
                 flag++;
+            }else{
+                BRANCH(13+100);
             }
         }
 
         StringBuilder sb = new StringBuilder();
-        if (aIsNegative ^ bIsNegative)
+        if (aIsNegative ^ bIsNegative){
+            BRANCH(14+100);
             sb.append('-');
+        }else{
+            BRANCH(15+100);
+        }
+
         boolean zeroCheck = true;
         for (Integer s : res) {
-            if (zeroCheck && s.equals(0))
+            BRANCH(16+100);
+            if (zeroCheck && s.equals(0)){
+                BRANCH(17+100);
                 continue;
+            }else{
+                BRANCH(18+100);
+            }
             zeroCheck = false;
             sb.append(s);
         }

diff --git a/test/com/jwetherell/algorithms/mathematics/test/MathematicsTest.java b/test/com/jwetherell/algorithms/mathematics/test/MathematicsTest.java
@@ -155,6 +155,21 @@ public void multiplication() {
             assertTrue("Multiplication using loop with int input. a=" + a + " b=" + b + " result=" + result + " check=" + check, (result == check));
         }
     }
+    @Test
+    public void testMultiplicationUsingFFTZero(){
+       long result = Integer.parseInt(Multiplication.multiplyUsingFFT("0", "0"));
+       long expected = 0;
+
+       assertTrue(result == expected);
+    }
+
+    @Test
+    public void testMultiplyUsingLoopsWithStringInputZero(){
+       long result = Integer.parseInt(Multiplication.multiplyUsingLoopWithStringInput("0", "0"));
+       long expected = 0;
+
+       assertTrue(result ==expected);
+   }
 
     @Test
     public void division() {
@@ -309,4 +324,3 @@ public void millerRabin() {
             assertFalse("Miller-Rabin test error. " + composite, Primes.millerRabinTest(composite));
     }
 }
-