Add test showing bug in IsProbablyDuplicate()

src/crypto/equihash.tcc

@@ -22,6 +22,28 @@ bool DistinctIndices(const FullStepRow<WIDTH>& a, const FullStepRow<WIDTH>& b, s
     return true;
 }
 
+template<size_t MAX_INDICES>
+bool IsProbablyDuplicate(std::shared_ptr<eh_trunc> indices, size_t lenIndices)
+{
+    assert(lenIndices <= MAX_INDICES);
+    bool checked_index[MAX_INDICES] = {false};
+    bool count_checked = 0;
+    for (int z = 0; z < lenIndices; z++) {
+        // Skip over indices we have already paired
+        if (!checked_index[z]) {
+            for (int y = z+1; y < lenIndices; y++) {
+                if (!checked_index[y] && indices.get()[z] == indices.get()[y]) {
+                    // Pair found
+                    checked_index[y] = true;
+                    count_checked += 2;
+                    break;
+                }
+            }
+        }
+    }
+    return count_checked == lenIndices;
+}
+
 template<size_t WIDTH>
 bool IsValidBranch(const FullStepRow<WIDTH>& a, const size_t len, const unsigned int ilen, const eh_trunc t)
 {