From 6149e6ba6be2d253384d34196826b26c8287610b Mon Sep 17 00:00:00 2001
From: Haidong Ji
Date: Sun, 10 May 2020 17:56:56 -0500
Subject: Reachability done!

---
 sources/__init__.py        |  0
 sources/reachability.py    | 37 +++++++++++++++++++++++++++++++++++++
 tests/__init__.py          |  0
 tests/test_reachability.py | 14 ++++++++++++++
 4 files changed, 51 insertions(+)
 create mode 100644 sources/__init__.py
 create mode 100644 sources/reachability.py
 create mode 100644 tests/__init__.py
 create mode 100644 tests/test_reachability.py

diff --git a/sources/__init__.py b/sources/__init__.py
new file mode 100644
index 0000000..e69de29
diff --git a/sources/reachability.py b/sources/reachability.py
new file mode 100644
index 0000000..07bb9df
--- /dev/null
+++ b/sources/reachability.py
@@ -0,0 +1,37 @@
+#Uses python3
+
+import sys
+
+
+def explore(adj, visited, x, y):
+    visited.append(x)
+    if x == y:
+        return
+    for i in adj[x]:
+        if i not in visited:
+            explore(adj, visited, i, y)
+
+
+def reach(adj, x, y):
+    visited = []
+    if x == y:
+        return 1
+    explore(adj, visited, x, y)
+    if y in visited:
+        return 1
+    return 0
+
+
+if __name__ == '__main__':
+    input = sys.stdin.read()
+    data = list(map(int, input.split()))
+    n, m = data[0:2]
+    data = data[2:]
+    edges = list(zip(data[0:(2 * m):2], data[1:(2 * m):2]))
+    x, y = data[2 * m:]
+    adj = [[] for _ in range(n)]
+    x, y = x - 1, y - 1
+    for (a, b) in edges:
+        adj[a - 1].append(b - 1)
+        adj[b - 1].append(a - 1)
+    print(reach(adj, x, y))
diff --git a/tests/__init__.py b/tests/__init__.py
new file mode 100644
index 0000000..e69de29
diff --git a/tests/test_reachability.py b/tests/test_reachability.py
new file mode 100644
index 0000000..318309b
--- /dev/null
+++ b/tests/test_reachability.py
@@ -0,0 +1,14 @@
+import unittest
+from sources.reachability import reach
+
+
+class TestReachability(unittest.TestCase):
+
+    def testName(self):
+        adj = [[1, 3],[], [1],[2]]
+        self.assertEqual(1, reach(adj, 0, 3))
+
+
+if __name__ == "__main__":
+    #import sys;sys.argv = ['', 'Test.testName']
+    unittest.main()
\ No newline at end of file
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