Finding the number of islands

Pranav Bhat · Pranav Bhat · commit 1ceb16f3b80e · 2019-12-02T13:19:50.000+05:30
diff --git a/ideserve_online/findNumberOfIslands.py b/ideserve_online/findNumberOfIslands.py
@@ -0,0 +1,59 @@
+
+from unittest import main, TestCase
+
+
+def printMatrix(mat):
+    print('-----------------------------')
+    for row in mat:
+        print(row)
+
+
+def visit(visited, i, j, mi, mj, mat):
+    if i < mi and j < mj:
+        visited[i][j] = True
+    nr = [-1, -1, -1, 0, 0, 1, 1, 1]
+    nc = [-1, 0, 1, -1, 1, -1, 0, 1]
+    for ro in nr:
+        for co in nc:
+            r = i + ro
+            c = j + co
+            if r >= 0 and r < mi and c >= 0 and c < mj and not visited[r][c] and mat[r][c]:
+                visited = visit(visited, r, c, mi, mj, mat)
+    return visited
+
+
+def findNumberOfIslands(mat):
+    visited = [[False for k in mat[0]] for p in mat]
+    count = 0
+    rows = len(mat)
+    cols = 0
+    if rows:
+        cols = len(mat[0])
+    for i in range(rows):
+        for j in range(cols):
+            if mat[i][j] and not visited[i][j]:
+                count += 1
+                visited = visit(visited, i, j, rows, cols, mat)
+    return count
+
+
+class CodeTest(TestCase):
+    def testEmpty(self):
+        self.assertEqual(findNumberOfIslands([]), 0)
+
+    def testNoIslands(self):
+        mat = [
+            [0, 0, 0, 0, 0, 0] * 8
+        ]
+        self.assertEqual(findNumberOfIslands(mat), 0)
+
+    def testSquare(self):
+        mat = [[1, 1, 0, 0, 0],
+               [0, 1, 0, 0, 1],
+               [1, 0, 0, 1, 1],
+               [0, 0, 0, 0, 0],
+               [1, 0, 1, 0, 1]]
+        self.assertEqual(findNumberOfIslands(mat), 5)
+
+
+main()
