Create find_peak-2d.py

Author: careermonk

src/chapter18divideandconquer/find_peak-2d.py

@@ -0,0 +1,40 @@
+import random
+import pprint
+
+def peak_find_2d(matrix):
+    j = len(matrix[0]) // 2
+
+    # maxvalue is the global maximum in column j
+    # rowmax is the row index of the maxvalue
+    maxvalue, rowmax = -1, -1
+    for row in range(len(matrix)):
+        if maxvalue <= matrix[row][j]:
+            maxvalue = matrix[row][j]
+            rowmax = row
+    print(rowmax, j, maxvalue)
+
+    left, right = 0, 0
+    if j > 0:
+        left = matrix[rowmax][j - 1]
+    if j < len(matrix[0]) - 1:
+        right = matrix[rowmax][j + 1]
+    if left <= maxvalue >= right:
+        return (rowmax, j, maxvalue)
+    if left > maxvalue:
+        half = []
+        for row in matrix:
+            half.append(row[:j + 1])
+        return peak_find_2d(half)
+    if right > maxvalue:
+        half = []
+        for row in matrix:
+            half.append(row[j:])
+        return peak_find_2d(half)
+
+def generate_2d_array(n=7, m=7, lower=0, upper=9):
+    return [[random.randint(lower, upper) for _ in range(m)] for _ in range(n)]
+
+if __name__ == '__main__':
+    matrix = generate_2d_array(upper=9)
+    pprint.pprint(matrix)
+    peak_find_2(matrix)