diff --git a/.gitignore b/.gitignore
index 6771c847..320dd40d 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,3 +1,4 @@
 /config.py
 __pycache__
 /comb.xml
+/hello.*
\ No newline at end of file
diff --git a/comb.py b/comb.py
index 5b0a9bec..bef81735 100644
--- a/comb.py
+++ b/comb.py
@@ -3,6 +3,8 @@
 import re
 import time
 import logging
+from gi.repository import GLib
+import pathlib
 
 import marisa_trie
 
diff --git a/graph.py b/graph.py
new file mode 100644
index 00000000..aa8a4518
--- /dev/null
+++ b/graph.py
@@ -0,0 +1,146 @@
+import sys
+from typing import Dict, List
+
+import marisa_trie
+from comb import SystemDict
+
+
+class Node:
+    def __init__(self, start_pos, word):
+        self.start_pos = start_pos
+        self.word = word
+        self.cost = -len(word)
+        self.prev = None
+
+    def __repr__(self):
+        return f"<Node: start_pos={self.start_pos}, word={self.word}, cost={self.cost}, prev={self.prev.word if self.prev else '-'}>"
+
+    def get_cost(self):
+        return - len(self.word)
+
+    def is_bos(self):
+        return self.word == '<S>'
+
+    def is_eos(self):
+        return self.word == '</S>'
+
+
+def create_graph(size: int) -> Dict[int, List[Node]]:
+    return {
+        0: [Node(start_pos=-9999, word='<S>')],
+        size: [Node(start_pos=-2, word='</S>')],
+    }
+
+
+def lookup(s, d: SystemDict):
+    for i in range(0, len(s)):
+        substr = s[i:]
+        words = d.trie.prefixes(substr)
+        for word in words:
+            print(f"+-+-+-= {d.trie[word]}")
+            yield word, d.trie[word][0].decode('utf-8').split('/') + [word]
+
+
+# n文字目でおわる単語リストを作成する
+def graph_construct(s, ht):
+    graph = create_graph(len(s))
+    print(graph)
+
+    for i in range(0, len(s)):
+        for j in range(i + 1, min(len(s) + 1, 16)):
+            substr = s[i:j]
+            if substr in ht:
+                for word in ht[substr]:
+                    node = Node(i, word)
+                    if j not in graph:
+                        graph[j] = []
+                    # print(f"graph[{j}]={graph[j]} graph={graph}")
+                    graph[j].append(node)
+
+    return graph
+
+
+def node_list(graph, i):
+    return graph[i]
+
+
+def get_prev_node(graph, node: Node) -> List[Node]:
+    if node.is_eos():
+        return graph[len(graph) - 1]
+    else:
+        return graph[node.start_pos]
+
+
+# TODO: エッジコスト的なももも考慮されたい。
+
+def viterbi(graph):
+    print("Viterbi phase 1")
+    for i in range(1, len(graph)):
+        nodes = node_list(graph, i)
+        for node in nodes:
+            node_cost = node.get_cost()
+            cost = sys.maxsize
+            shortest_prev = None
+            prev_nodes = get_prev_node(graph, node)
+            if prev_nodes[0].is_bos():
+                pass
+            else:
+                for prev_node in prev_nodes:
+                    tmp_cost = prev_node.cost + node_cost
+                    if tmp_cost < cost:
+                        cost = tmp_cost
+                        shortest_prev = prev_node
+                node.prev = shortest_prev
+                node.cost = cost
+
+    dump_graph(graph)
+    # sys.exit(1) # XXXXXXXXXXXXXXXX
+
+    print("Viterbi phase 2")
+    node = graph[len(graph) - 1][0]
+    result = []
+    while not node.is_bos():
+        result.append(node)
+        node = node.prev
+    return reversed(result)
+
+
+def dump_graph(graph):
+    with open('hello.dot', 'w') as fp:
+        fp.write("""digraph graph_name {\n""")
+        fp.write("""  graph [\n""")
+        fp.write("""    charset="utf-8"\n""")
+        fp.write("""  ]\n""")
+        for i, nodes in graph.items():
+            for node in nodes:
+                if node.is_eos():
+                    fp.write(f"""  {i} -> {i} [label="{node.word}"]\n""")
+                else:
+                    fp.write(f"""  {node.start_pos} -> {i} [label="{node.word}"]\n""")
+        fp.write("""}\n""")
+
+
+# TODO: generate diagram via graphviz...
+def main():
+    src = 'きょうは'
+    if False:
+        system_dict = SystemDict()
+        ht = dict(lookup(src, system_dict))
+    else:
+        ht = {
+            'き': ['木', '気', 'き'],
+            'きょ': ['虚', 'きょ'],
+            'きょう': ['今日', 'きょう'],
+            'ょ': ['ょ'],
+            'ょう': ['ょう'],
+            'う': ['う'],
+            'は': ['葉', 'は'],
+            'うは': ['右派', 'うは'],
+        }
+    print(ht)
+    graph = graph_construct(src, ht)
+    print(graph)
+    print(viterbi(graph))
+
+
+main()