diff --git a/src/analyse/backtrack.cc b/src/analyse/backtrack.cc
index af81378..5b7422a 100644
--- a/src/analyse/backtrack.cc
+++ b/src/analyse/backtrack.cc
@@ -5,32 +5,54 @@
 #include <set>
 #include <unordered_set>
 
+#include <algorithm>
+
 #include "common_code.h"
 
 // TODO: using const RawCode& instead of uint64_t
 
-namespace std {
-    template<>
-    struct hash<Analyse::backtrack_t> {
-        std::size_t operator()(const Analyse::backtrack_t &b) const {
-            std::cout << "get hash: " << b.code << std::endl;
-            return std::hash<uint64_t>()(b.code);
+//namespace std {
+//    template<>
+//    struct hash<Analyse::backtrack_t> {
+//        std::size_t operator()(const Analyse::backtrack_t &b) const {
+//            std::cout << "get hash: " << b.code << std::endl;
+//            return std::hash<uint64_t>()(b.code);
+//        }
+//    };
+//
+//    template<>
+//    struct equal_to<Analyse::backtrack_t> {
+//        bool operator()(const Analyse::backtrack_t &b1, const Analyse::backtrack_t &b2) const {
+//            std::cout << "get eq: " << b1.code << " ? " << b2.code << std::endl;
+//            return b1.code == b2.code;
+//        }
+//    };
+//}
+
+void Analyse::backtrack_demo(const std::vector<uint64_t> &codes) {
+
+
+    std::vector<std::vector<analyse_t*>> todos;
+
+    for (const auto &code : codes) {
+
+        auto c = cases.find(code);
+
+        if (c == cases.end()) {
+            // TODO: invalid input
+            return;
         }
-    };
 
-    template<>
-    struct equal_to<Analyse::backtrack_t> {
-        bool operator()(const Analyse::backtrack_t &b1, const Analyse::backtrack_t &b2) const {
-            std::cout << "get eq: " << b1.code << " ? " << b2.code << std::endl;
-            return b1.code == b2.code;
+        if (c->second.step >= todos.size()) {
+            todos.resize(c->second.step + 1);
         }
-    };
-}
 
-void Analyse::backtrack_demo(const std::vector<uint64_t> &codes) {
+        todos[c->second.step].emplace_back(&c->second);
+
+    }
+
+    std::reverse(todos.begin(), todos.end());
 
-    // TODO: confirm code exist
-//    std::cout << cases[code].step << std::endl;
 
     struct cache_t {
         analyse_t *a;
@@ -40,61 +62,73 @@ void Analyse::backtrack_demo(const std::vector<uint64_t> &codes) {
     std::queue<cache_t> track_cache;
     std::vector<std::unordered_map<uint64_t, backtrack_t>> track_data;
 
-    track_data.resize(82); // TODO: setting as (max steps + 1)
+//    track_data.resize(82); // TODO: setting as (max steps + 1)
 
+    track_data.resize(todos.size());
 
     // TODO: for diff layer cases, layer_num from big to small -> if found then skip search
 
-    for (const auto &code : codes) {
-
-        auto &cc = cases[code];
+    for (const auto &todo : todos) {
 
-        /// enlarge track_data
-        if (cc.step >= track_data.size()) {
-            track_data.resize(cc.step + 1);
+        if (todo.empty()) {
+            continue;
         }
 
-        track_cache.emplace(cache_t {
-            .a = &cc,
-            .b = &track_data[cc.step].emplace(code, backtrack_t {
-                .code = code,
-                .layer_num = cc.step,
-                .last = std::list<backtrack_t*>{},
-                .next = std::list<backtrack_t*>{},
-            }).first->second,
-        });
+        /// clear track cache
+        std::queue<cache_t>{}.swap(track_cache);
 
-    }
+        for (const auto c : todo) {
+
+            // TODO: if c already exist -> skip
+            if (track_data[c->step].find(c->code) == track_data[c->step].end()) {
 
-    while (!track_cache.empty()) {
-        /// handle first element and pop it
-        auto curr = track_cache.front();
-        for (auto src : curr.a->src) { // traverse src cases of current node
-            auto t_src = track_data[src->step].find(src->code);
-            if (t_src != track_data[src->step].end()) { // match src case
-                /// link (curr.b) and (t_src->second)
-                t_src->second.next.emplace_back(curr.b);
-                curr.b->last.emplace_back(&t_src->second);
-            } else { // src case not found
-                /// link (curr.b) and (t_src_new->second)
-                auto t_src_new = track_data[src->step].emplace(src->code, backtrack_t {
-                    .code = src->code,
-                    .layer_num = src->step,
-                    .last = std::list<backtrack_t*>{},
-                    .next = std::list<backtrack_t*>{curr.b}, // link to curr.b
-                }).first;
-                curr.b->last.emplace_back(&t_src_new->second);
-                /// insert into working queue
-                track_cache.emplace(cache_t {
-                    .a = src,
-                    .b = &t_src_new->second,
+                track_cache.emplace(cache_t{
+                    .a = c,
+                    .b = &track_data[c->step].emplace(c->code, backtrack_t{
+                        .code = c->code,
+                        .layer_num = c->step,
+                        .last = std::list<backtrack_t *>{},
+                        .next = std::list<backtrack_t *>{},
+                    }).first->second,
                 });
             }
+
+        }
+
+
+        while (!track_cache.empty()) {
+            /// handle first element and pop it
+            auto curr = track_cache.front();
+            for (auto src : curr.a->src) { // traverse src cases of current node
+                auto t_src = track_data[src->step].find(src->code);
+                if (t_src != track_data[src->step].end()) { // match src case
+                    /// link (curr.b) and (t_src->second)
+                    t_src->second.next.emplace_back(curr.b);
+                    curr.b->last.emplace_back(&t_src->second);
+                } else { // src case not found
+                    /// link (curr.b) and (t_src_new->second)
+                    auto t_src_new = track_data[src->step].emplace(src->code, backtrack_t {
+                        .code = src->code,
+                        .layer_num = src->step,
+                        .last = std::list<backtrack_t*>{},
+                        .next = std::list<backtrack_t*>{curr.b}, // link to curr.b
+                    }).first;
+                    curr.b->last.emplace_back(&t_src_new->second);
+                    /// insert into working queue
+                    track_cache.emplace(cache_t {
+                        .a = src,
+                        .b = &t_src_new->second,
+                    });
+                }
+            }
+            track_cache.pop();
         }
-        track_cache.pop();
+
+
     }
 
 
+
     for (uint32_t i = 0; i < track_data.size(); ++i) {
 
         const auto &ly = track_data[i];