Merge pull request #310 from Sankalp7943/sankalp/arrays

chore(Python): add sankalp arrays

algorithms/Python/README.md

@@ -2,6 +2,9 @@
 
 ## Arrays
 1. [Count Inversions](arrays/counting_inversions.py)
+2. [Majority Element](arrays/majority_element.py)
+3. [Rotate Array](arrays/rotate_array.py)
+4. [Missing Number](arrays/missing_number.py)
 
 ## Linked Lists
 1. [Doubly](linked_lists/doubly.py)

algorithms/Python/arrays/majority_element.py

@@ -0,0 +1,26 @@
+"""
+Algorithm Type: Array Traversal
+Time Complexity: O(n)
+"""
+numbers = [2, 2, 5, 6, 2, 6, 2, 10, 2]
+
+def majority_element(numbers):
+    m = float("inf")
+    cnt = 0
+    for num in numbers:
+        if cnt == 0:
+            m = num
+            cnt += 1
+        elif m == num:
+            cnt += 1
+        else:
+            cnt -= 1
+    # to verify the most frequent number is greater than length of aaray//2
+    recheck_cnt = 0
+    for num in numbers:
+        if num == m:
+            recheck_cnt += 1
+    return m if recheck_cnt > len(numbers)//2 else None
+
+if __name__ == "__main__":
+  print(majority_element(numbers))

algorithms/Python/arrays/missing_number.py

@@ -0,0 +1,15 @@
+"""
+Algorithm Type: Array Traversal
+Time Complexity: O(n)
+"""
+numbers = [1, 2, 4, 3, 6, 7, 9, 8, 10]
+n = 10
+
+def missing_number(numbers, n):
+    s = sum(numbers)
+    expected_s = (n*(n+1))//2 #for C++ or similar, keep in mind expected_s can overflow MAX INT limit.
+    return expected_s - s
+
+
+if __name__ == "__main__":
+  print(missing_number(numbers, n))

algorithms/Python/arrays/rotate_array.py

@@ -0,0 +1,26 @@
+"""
+Algorithm Type: Array Traversal
+Time Complexity: O(n)
+"""
+numbers = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
+k = 3
+
+def rotate_array(numbers, k):
+    n = len(numbers)
+    k = k % n
+    if k == 0:
+        return numbers
+    for i in range(n-k):
+        if i>((n-k)//2):
+            break
+        numbers[i], numbers[n-k-(i+1)] = numbers[n-k-(i+1)], numbers[i]
+
+    for i in range(k):
+        if i>k//2:
+            break
+        numbers[-1-i], numbers[-k+i] = numbers[-k+i], numbers[-1-i]
+    reversed_numbers = numbers[::-1]
+    return reversed_numbers
+
+if __name__ == "__main__":
+  print(rotate_array(numbers, k))