Created check_bipartite.py in algorithms/graph + test cases (keon#347)

* Update __init__.py

* Update test_graph.py

* Create check_bipartite.py

* Update README.md

* Update README_CN.md

* Update README_GE.md

* Update README_JP.md

* Update README_KR.md

* Update check_bipartite.py

* Update check_bipartite.py

Author: geon0325

README.md

@@ -139,6 +139,7 @@ If you want to uninstall algorithms, it is as simple as:
     - [word_break](algorithms/dp/word_break.py)
     - [fibonacci](algorithms/dp/fib.py)
 - [graph](algorithms/graph)
+    - [check_bipartite](algorithms/graph/check_bipartite.py)
     - [strongly_connected](algorithms/graph/checkDiGraphStronglyConnected.py)
     - [clone_graph](algorithms/graph/clone_graph.py)
     - [cycle_detection](algorithms/graph/cycle_detection.py)

README_CN.md

@@ -142,6 +142,7 @@ pip3 uninstall -y algorithms
     - [regex_matching：正则匹配](algorithms/dp/regex_matching.py)
     - [word_break：单词分割](algorithms/dp/word_break.py)
 - [graph：图](graph)
+    - [check_bipartite](algorithms/graph/check_bipartite.py)
     - [2-sat：2-sat](algorithms/graph/satisfiability.py)
     - [clone_graph：克隆图](algorithms/graph/clone_graph.py)
     - [cycle_detection：判断圈算法](algorithms/graph/cycle_detection.py)

README_GE.md

@@ -146,6 +146,7 @@ Um das Projekt zu deinstallieren tippen Sie folgendes:
     - [word_break](algorithms/dp/word_break.py)
     - [fibonacci](algorithms/dp/fib.py)
 - [graph](algorithms/graph)
+    - [check_bipartite](algorithms/graph/check_bipartite.py)
     - [strongly_connected](algorithms/graph/checkDiGraphStronglyConnected.py)
     - [clone_graph](algorithms/graph/clone_graph.py)
     - [cycle_detection](algorithms/graph/cycle_detection.py)

README_JP.md

@@ -140,6 +140,7 @@ if __name__ == "__main__":
     - [word_break](algorithms/dp/word_break.py)
     - [fibonacci](algorithms/dp/fib.py)
 - [graph : グラフ](algorithms/graph)
+    - [check_bipartite](algorithms/graph/check_bipartite.py)
     - [strongly_connected](algorithms/graph/checkDiGraphStronglyConnected.py)
     - [clone_graph](algorithms/graph/clone_graph.py)
     - [cycle_detection](algorithms/graph/cycle_detection.py)

README_KR.md

@@ -137,6 +137,7 @@ if __name__ == "__main__":
     - [word_break](algorithms/dp/word_break.py)
     - [fibonacci](algorithms/dp/fib.py)
 - [graph : 그래프](algorithms/graph)
+    - [check_bipartite](algorithms/graph/check_bipartite.py)
     - [strongly_connected](algorithms/graph/checkDiGraphStronglyConnected.py)
     - [clone_graph](algorithms/graph/clone_graph.py)
     - [cycle_detection](algorithms/graph/cycle_detection.py)

algorithms/graph/__init__.py

@@ -1 +1,2 @@
 from .tarjan import *
+from .check_bipartite import *

algorithms/graph/check_bipartite.py

@@ -0,0 +1,39 @@
+"""
+
+Bipartite graph is a graph whose vertices can be divided into two disjoint and independent sets.
+(https://en.wikipedia.org/wiki/Bipartite_graph)
+
+Time complexity is O(|E|)
+Space complexity is O(|V|)
+
+"""
+
+def check_bipartite(adj_list):
+
+    V = len(adj_list)
+
+    # Divide vertexes in the graph into set_type 1 and 2
+    # Initialize all set_types as -1
+    set_type = [-1 for v in range(V)]
+    set_type[0] = 0
+
+    q = [0]
+
+    while q:
+        v = q.pop(0)
+
+        # If there is a self-loop, it cannot be bipartite
+        if adj_list[v][v]:
+            return False
+
+        for u in range(V):
+            if adj_list[v][u]:
+                if set_type[u] == set_type[v]:
+                    return False
+                elif set_type[u] == -1:
+                    # set type of u opposite of v
+                    set_type[u] = 1 - set_type[v]
+                    q.append(u)
+
+    return True
+

tests/test_graph.py

@@ -1,4 +1,5 @@
 from algorithms.graph import Tarjan
+from algorithms.graph import check_bipartite
 
 import unittest
 
@@ -42,3 +43,17 @@ def test_tarjan_example_2(self):
 
         g = Tarjan(example)
         self.assertEqual(g.sccs, [['A', 'B', 'E'], ['C', 'D'], ['F', 'G'], ['H']])
+
+        
+class TestCheckBipartite(unittest.TestCase):
+    
+    def test_check_bipartite(self):
+        
+        adj_list_1 = [[0, 0, 1], [0, 0, 1], [1, 1, 0]]
+        self.assertEqual(True, check_bipartite(adj_list_1))
+        
+        adj_list_2 = [[0, 1, 0, 1], [1, 0, 1, 0], [0, 1, 0, 1], [1, 0, 1, 0]]
+        self.assertEqual(True, check_bipartite(adj_list_2))
+        
+        adj_list_3 = [[0, 1, 0, 0], [1, 0, 1, 1], [0, 1, 0, 1], [0, 1, 1, 0]]
+        self.assertEqual(False, check_bipartite(adj_list_3))