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searching/binary_search.py

@@ -0,0 +1,70 @@
+#!/usr/bin/env python3
+# -*- coding: utf-8 -*-
+# author: bt3gl
+
+
+def binary_search_recursive(array, item, higher=None, lower=0):
+
+    higher = higher or len(array)
+    if higher < lower:
+        return False
+    
+    mid = (higher + lower)//2
+    if  item == array[mid]:
+        return mid
+    elif item < array[mid]:
+        return binary_search_recursive(array, item, higher=mid-1, lower=lower)
+    else:
+        return binary_search_recursive(array, item, higher=higher, lower=mid+1)
+
+
+def binary_search_iterative(array, item):
+    lower, higher = 0, len(array)
+
+    while lower < higher:
+        mid = (higher+lower)//2
+        if array[mid] == item:
+            return mid
+        elif array[mid] > item:
+            higher = mid
+        else:
+            lower=mid+1
+    return False
+
+
+def binary_search_matrix(matrix, item, lower=0, higher=None):
+    """ Binary search in a matrix """
+
+    if not matrix:
+        return None
+    
+    rows = len(matrix)
+    cols = len(matrix[0])
+    higher = higher or rows*cols
+
+    if higher > lower:
+        mid = (higher + lower)//2
+        row = mid//cols
+        col = mid%cols
+        item = matrix[row][col]
+
+        if item == item:
+            return row, col
+        elif item < item:
+            return binary_search_matrix(matrix, item, lower, mid-1)
+        else:
+            return binary_search_matrix(matrix, item, mid+1, higher)
+        
+    return None
+
+
+if __name__ == '__main__':
+
+    array = [2, 3, 5, 6, 8, 10, 15, 23]
+    matrix = [[1, 2, 3], [4, 5, 6], [7, 8, 9]]
+    item = 15
+    
+    print('Recursive: ', binary_search_recursive(array, item))
+    print('Iterative: ', binary_search_iterative(array, item))
+    print('Matrix: ', binary_search_matrix(matrix, item))
+