diff --git a/native/jni/src/suggest/policyimpl/dictionary/dynamic_patricia_trie_gc_event_listeners.cpp b/native/jni/src/suggest/policyimpl/dictionary/dynamic_patricia_trie_gc_event_listeners.cpp
index 9b82673..ffa02e3 100644
--- a/native/jni/src/suggest/policyimpl/dictionary/dynamic_patricia_trie_gc_event_listeners.cpp
+++ b/native/jni/src/suggest/policyimpl/dictionary/dynamic_patricia_trie_gc_event_listeners.cpp
@@ -20,7 +20,8 @@
 
 bool DynamicPatriciaTrieGcEventListeners
         ::ListenerForUpdatingUnigramProbabilityAndMarkingUselessPtNodesAsDeleted
-                ::onVisitingPtNode(const DynamicPatriciaTrieNodeReader *const node) {
+                ::onVisitingPtNode(const DynamicPatriciaTrieNodeReader *const node,
+                        const int *const nodeCodePoints) {
     // PtNode is useless when the PtNode is not a terminal and doesn't have any not useless
     // children.
     bool isUselessPtNode = !node->isTerminal();
@@ -45,4 +46,53 @@
     return true;
 }
 
+// Writes dummy PtNode array size when the head of PtNode array is read.
+bool DynamicPatriciaTrieGcEventListeners::ListenerForPlacingAndWritingValidPtNodesToBuffer
+        ::onDescend(const int ptNodeArrayPos) {
+    mValidPtNodeCount = 0;
+    int writingPos = mBufferToWrite->getTailPosition();
+    mPositionMap->insert(hash_map_compat<int, int>::value_type(ptNodeArrayPos,  writingPos));
+    // Writes dummy PtNode array size because arrays can have a forward link or needles PtNodes.
+    // This field will be updated later in onReadingPtNodeArrayTail() with actual PtNode count.
+    mPtNodeArraySizeFieldPos = writingPos;
+    return DynamicPatriciaTrieWritingUtils::writePtNodeArraySizeAndAdvancePosition(
+            mBufferToWrite, 0 /* arraySize */, &writingPos);
+}
+
+// Write PtNode array terminal and actual PtNode array size.
+bool DynamicPatriciaTrieGcEventListeners::ListenerForPlacingAndWritingValidPtNodesToBuffer
+        ::onReadingPtNodeArrayTail() {
+    int writingPos = mBufferToWrite->getTailPosition();
+    // Write PtNode array terminal.
+    if (!DynamicPatriciaTrieWritingUtils::writeForwardLinkPositionAndAdvancePosition(
+            mBufferToWrite, NOT_A_DICT_POS /* forwardLinkPos */, &writingPos)) {
+        return false;
+    }
+    // Write actual PtNode array size.
+    if (!DynamicPatriciaTrieWritingUtils::writePtNodeArraySizeAndAdvancePosition(
+            mBufferToWrite, mValidPtNodeCount, &mPtNodeArraySizeFieldPos)) {
+        return false;
+    }
+    return true;
+}
+
+// Write valid PtNode to buffer and memorize mapping from the old position to the new position.
+bool DynamicPatriciaTrieGcEventListeners::ListenerForPlacingAndWritingValidPtNodesToBuffer
+        ::onVisitingPtNode(const DynamicPatriciaTrieNodeReader *const node,
+                const int *const nodeCodePoints) {
+    if (node->isDeleted()) {
+        // Current PtNode is not written in new buffer because it has been deleted.
+        mPositionMap->insert(hash_map_compat<int, int>::value_type(node->getHeadPos(),
+                NOT_A_DICT_POS));
+        return true;
+    }
+    int writingPos = mBufferToWrite->getTailPosition();
+    mPositionMap->insert(hash_map_compat<int, int>::value_type(node->getHeadPos(), writingPos));
+    mValidPtNodeCount++;
+    // Writes current PtNode.
+    return mWritingHelper->writePtNodeToBufferByCopyingPtNodeInfo(mBufferToWrite, node,
+            node->getParentPos(),  nodeCodePoints, node->getCodePointCount(),
+            node->getProbability(), &writingPos);
+}
+
 } // namespace latinime
diff --git a/native/jni/src/suggest/policyimpl/dictionary/dynamic_patricia_trie_gc_event_listeners.h b/native/jni/src/suggest/policyimpl/dictionary/dynamic_patricia_trie_gc_event_listeners.h
index f08a2c5..7285593 100644
--- a/native/jni/src/suggest/policyimpl/dictionary/dynamic_patricia_trie_gc_event_listeners.h
+++ b/native/jni/src/suggest/policyimpl/dictionary/dynamic_patricia_trie_gc_event_listeners.h
@@ -24,6 +24,8 @@
 #include "suggest/policyimpl/dictionary/dynamic_patricia_trie_reading_helper.h"
 #include "suggest/policyimpl/dictionary/dynamic_patricia_trie_writing_helper.h"
 #include "suggest/policyimpl/dictionary/dynamic_patricia_trie_writing_utils.h"
+#include "suggest/policyimpl/dictionary/utils/buffer_with_extendable_buffer.h"
+#include "utils/hash_map_compat.h"
 
 namespace latinime {
 
@@ -52,12 +54,15 @@
             return true;
         }
 
-        bool onDescend() {
+        bool onDescend(const int ptNodeArrayPos) {
             valueStack.push_back(0);
             return true;
         }
 
-        bool onVisitingPtNode(const DynamicPatriciaTrieNodeReader *const node);
+        bool onReadingPtNodeArrayTail() { return true; }
+
+        bool onVisitingPtNode(const DynamicPatriciaTrieNodeReader *const node,
+                const int *const nodeCodePoints);
 
      private:
         DISALLOW_IMPLICIT_CONSTRUCTORS(
@@ -79,9 +84,12 @@
 
         bool onAscend() { return true; }
 
-        bool onDescend() { return true; }
+        bool onDescend(const int ptNodeArrayPos) { return true; }
 
-        bool onVisitingPtNode(const DynamicPatriciaTrieNodeReader *const node) {
+        bool onReadingPtNodeArrayTail() { return true; }
+
+        bool onVisitingPtNode(const DynamicPatriciaTrieNodeReader *const node,
+                const int *const nodeCodePoints) {
             if (!node->isDeleted()) {
                 int pos = node->getBigramsPos();
                 if (pos != NOT_A_DICT_POS) {
@@ -99,6 +107,40 @@
         DynamicBigramListPolicy *const mBigramPolicy;
     };
 
+    class ListenerForPlacingAndWritingValidPtNodesToBuffer
+            : public DynamicPatriciaTrieReadingHelper::TraversingEventListener {
+     public:
+        ListenerForPlacingAndWritingValidPtNodesToBuffer(
+                DynamicPatriciaTrieWritingHelper *const writingHelper,
+                BufferWithExtendableBuffer *const bufferToWrite,
+                hash_map_compat<int, int> *const positionMap)
+                : mWritingHelper(writingHelper), mBufferToWrite(bufferToWrite),
+                  mPositionMap(positionMap), mValidPtNodeCount(0),
+                  mPtNodeArraySizeFieldPos(NOT_A_DICT_POS) {};
+
+        bool onAscend() { return true; }
+
+        bool onDescend(const int ptNodeArrayPos);
+
+        bool onReadingPtNodeArrayTail();
+
+        bool onVisitingPtNode(const DynamicPatriciaTrieNodeReader *const node,
+                const int *const nodeCodePoints);
+
+        hash_map_compat<int, int> *getPositionMap() const {
+            return mPositionMap;
+        }
+
+     private:
+        DISALLOW_IMPLICIT_CONSTRUCTORS(ListenerForPlacingAndWritingValidPtNodesToBuffer);
+
+        DynamicPatriciaTrieWritingHelper *const mWritingHelper;
+        BufferWithExtendableBuffer *const mBufferToWrite;
+        hash_map_compat<int, int> *const mPositionMap;
+        int mValidPtNodeCount;
+        int mPtNodeArraySizeFieldPos;
+    };
+
  private:
     DISALLOW_IMPLICIT_CONSTRUCTORS(DynamicPatriciaTrieGcEventListeners);
 };
diff --git a/native/jni/src/suggest/policyimpl/dictionary/dynamic_patricia_trie_reading_helper.cpp b/native/jni/src/suggest/policyimpl/dictionary/dynamic_patricia_trie_reading_helper.cpp
index 10ab793..754b679 100644
--- a/native/jni/src/suggest/policyimpl/dictionary/dynamic_patricia_trie_reading_helper.cpp
+++ b/native/jni/src/suggest/policyimpl/dictionary/dynamic_patricia_trie_reading_helper.cpp
@@ -25,18 +25,22 @@
 const int DynamicPatriciaTrieReadingHelper::MAX_NODE_ARRAY_COUNT_TO_AVOID_INFINITE_LOOP = 100000;
 const size_t DynamicPatriciaTrieReadingHelper::MAX_READING_STATE_STACK_SIZE = MAX_WORD_LENGTH;
 
+// Visits all PtNodes in post-order depth first manner.
+// For example, visits c -> b -> y -> x -> a for the following dictionary:
+// a _ b _ c
+//   \ x _ y
 bool DynamicPatriciaTrieReadingHelper::traverseAllPtNodesInPostorderDepthFirstManner(
         TraversingEventListener *const listener) {
     bool alreadyVisitedChildren = false;
     // Descend from the root to the root PtNode array.
-    if (!listener->onDescend()) {
+    if (!listener->onDescend(getPosOfLastPtNodeArrayHead())) {
         return false;
     }
     while (!isEnd()) {
         if (!alreadyVisitedChildren) {
             if (mNodeReader.hasChildren()) {
                 // Move to the first child.
-                if (!listener->onDescend()) {
+                if (!listener->onDescend(mNodeReader.getChildrenPos())) {
                     return false;
                 }
                 pushReadingStateToStack();
@@ -45,13 +49,16 @@
                 alreadyVisitedChildren = true;
             }
         } else {
-            if (!listener->onVisitingPtNode(&mNodeReader)) {
+            if (!listener->onVisitingPtNode(&mNodeReader, mMergedNodeCodePoints)) {
                 return false;
             }
             readNextSiblingNode();
             if (isEnd()) {
                 // All PtNodes in current linked PtNode arrays have been visited.
                 // Return to the parent.
+                if (!listener->onReadingPtNodeArrayTail()) {
+                    return false;
+                }
                 if (!listener->onAscend()) {
                     return false;
                 }
@@ -70,6 +77,75 @@
     return !isError();
 }
 
+// Visits all PtNodes in PtNode array level pre-order depth first manner, which is the same order
+// that PtNodes are written in the dictionary buffer.
+// For example, visits a -> b -> x -> c -> y for the following dictionary:
+// a _ b _ c
+//   \ x _ y
+bool DynamicPatriciaTrieReadingHelper::traverseAllPtNodesInPtNodeArrayLevelPreorderDepthFirstManner(
+        TraversingEventListener *const listener) {
+    bool alreadyVisitedAllPtNodesInArray = false;
+    bool alreadyVisitedChildren = false;
+    // Descend from the root to the root PtNode array.
+    if (!listener->onDescend(getPosOfLastPtNodeArrayHead())) {
+        return false;
+    }
+    pushReadingStateToStack();
+    while (!isEnd()) {
+        if (alreadyVisitedAllPtNodesInArray) {
+            if (alreadyVisitedChildren) {
+                // Move to next sibling PtNode's children.
+                readNextSiblingNode();
+                if (isEnd()) {
+                    // Return to the parent PTNode.
+                    if (!listener->onAscend()) {
+                        return false;
+                    }
+                    popReadingStateFromStack();
+                    alreadyVisitedChildren = true;
+                    alreadyVisitedAllPtNodesInArray = true;
+                } else {
+                    alreadyVisitedChildren = false;
+                }
+            } else {
+                if (mNodeReader.hasChildren()) {
+                    // Move to the first child.
+                    if (!listener->onDescend(mNodeReader.getChildrenPos())) {
+                        return false;
+                    }
+                    pushReadingStateToStack();
+                    readChildNode();
+                    // Push state to return the head of PtNode array.
+                    pushReadingStateToStack();
+                    alreadyVisitedAllPtNodesInArray = false;
+                    alreadyVisitedChildren = false;
+                } else {
+                    alreadyVisitedChildren = true;
+                }
+            }
+        } else {
+            if (!listener->onVisitingPtNode(&mNodeReader, mMergedNodeCodePoints)) {
+                return false;
+            }
+            readNextSiblingNode();
+            if (isEnd()) {
+                if (!listener->onReadingPtNodeArrayTail()) {
+                    return false;
+                }
+                // Return to the head of current PtNode array.
+                popReadingStateFromStack();
+                alreadyVisitedAllPtNodesInArray = true;
+            }
+        }
+    }
+    popReadingStateFromStack();
+    // Ascend from the root PtNode array to the root.
+    if (!listener->onAscend()) {
+        return false;
+    }
+    return !isError();
+}
+
 // Read node array size and process empty node arrays. Nodes and arrays are counted up in this
 // method to avoid an infinite loop.
 void DynamicPatriciaTrieReadingHelper::nextPtNodeArray() {
diff --git a/native/jni/src/suggest/policyimpl/dictionary/dynamic_patricia_trie_reading_helper.h b/native/jni/src/suggest/policyimpl/dictionary/dynamic_patricia_trie_reading_helper.h
index 4974459..b033eee 100644
--- a/native/jni/src/suggest/policyimpl/dictionary/dynamic_patricia_trie_reading_helper.h
+++ b/native/jni/src/suggest/policyimpl/dictionary/dynamic_patricia_trie_reading_helper.h
@@ -45,10 +45,14 @@
         virtual bool onAscend() = 0;
 
         // Returns whether the event handling was succeeded or not.
-        virtual bool onDescend() = 0;
+        virtual bool onDescend(const int ptNodeArrayPos) = 0;
 
         // Returns whether the event handling was succeeded or not.
-        virtual bool onVisitingPtNode(const DynamicPatriciaTrieNodeReader *const node) = 0;
+        virtual bool onReadingPtNodeArrayTail() = 0;
+
+        // Returns whether the event handling was succeeded or not.
+        virtual bool onVisitingPtNode(const DynamicPatriciaTrieNodeReader *const node,
+                const int *const nodeCodePoints) = 0;
 
      protected:
         TraversingEventListener() {};
@@ -208,6 +212,9 @@
 
     bool traverseAllPtNodesInPostorderDepthFirstManner(TraversingEventListener *const listener);
 
+    bool traverseAllPtNodesInPtNodeArrayLevelPreorderDepthFirstManner(
+            TraversingEventListener *const listener);
+
  private:
     DISALLOW_COPY_AND_ASSIGN(DynamicPatriciaTrieReadingHelper);
 
diff --git a/native/jni/src/suggest/policyimpl/dictionary/dynamic_patricia_trie_writing_helper.cpp b/native/jni/src/suggest/policyimpl/dictionary/dynamic_patricia_trie_writing_helper.cpp
index 0d872f2..3fc9c4c 100644
--- a/native/jni/src/suggest/policyimpl/dictionary/dynamic_patricia_trie_writing_helper.cpp
+++ b/native/jni/src/suggest/policyimpl/dictionary/dynamic_patricia_trie_writing_helper.cpp
@@ -536,6 +536,13 @@
             &listenerForupdatingBigramProbability)) {
         return false;
     }
+
+    // Mapping from positions in mBuffer to positions in bufferToWrite.
+    hash_map_compat<int, int> positionMap;
+    readingHelper.initWithPtNodeArrayPos(rootPtNodeArrayPos);
+    DynamicPatriciaTrieGcEventListeners::ListenerForPlacingAndWritingValidPtNodesToBuffer
+            listenerForPlacingAndWritingLivingPtNodesToBuffer(this, mBuffer, &positionMap);
+
     // TODO: Implement.
     return false;
 }
diff --git a/native/jni/src/suggest/policyimpl/dictionary/dynamic_patricia_trie_writing_helper.h b/native/jni/src/suggest/policyimpl/dictionary/dynamic_patricia_trie_writing_helper.h
index d164e43..e82b80a 100644
--- a/native/jni/src/suggest/policyimpl/dictionary/dynamic_patricia_trie_writing_helper.h
+++ b/native/jni/src/suggest/policyimpl/dictionary/dynamic_patricia_trie_writing_helper.h
@@ -59,6 +59,13 @@
     // DynamicPatriciaTrieGcEventListeners.
     bool markNodeAsDeleted(const DynamicPatriciaTrieNodeReader *const nodeToUpdate);
 
+    // CAVEAT: This method must be called only from this class or inner classes of
+    // DynamicPatriciaTrieGcEventListeners.
+    bool writePtNodeToBufferByCopyingPtNodeInfo(BufferWithExtendableBuffer *const bufferToWrite,
+            const DynamicPatriciaTrieNodeReader *const originalNode, const int parentPos,
+            const int *const codePoints, const int codePointCount, const int probability,
+            int *const writingPos);
+
  private:
     DISALLOW_IMPLICIT_CONSTRUCTORS(DynamicPatriciaTrieWritingHelper);
 
@@ -82,11 +89,6 @@
             const int parentPos, const int *const codePoints, const int codePointCount,
             const int probability, int *const writingPos);
 
-    bool writePtNodeToBufferByCopyingPtNodeInfo(BufferWithExtendableBuffer *const bufferToWrite,
-            const DynamicPatriciaTrieNodeReader *const originalNode, const int parentPos,
-            const int *const codePoints, const int codePointCount, const int probability,
-            int *const writingPos);
-
     bool createAndInsertNodeIntoPtNodeArray(const int parentPos, const int *const nodeCodePoints,
             const int nodeCodePointCount, const int probability, int *const forwardLinkFieldPos);