added majority element problem to datastructures/arrays

data_structures/arrays/majority_element.py

@@ -0,0 +1,33 @@
+"""
+PROBLEM : Find majority element in the given array.
+PROBLEM DESCRIPTION :
+Given a array of elements of size n.
+The majority element is the element that appears more than [n/2] times.
+We assume that the majority element is always exists in the array.
+EXAMPLE :
+    input : array = [1,3,5,1,1]
+    output : 1
+    explanation : 1 appears three times in array,
+    which is greater than [n/2] i.e [5/2] = 2.
+APPROACH:
+- In an array of elements of size n,
+  there exists only one element that appears greater than [n/2] times.
+- If we sort the given elements in the array the [n/2]th
+   element in the array must be the majority element.
+- if we sort [1,3,5,1,1] it will be [1,1,1,3,5]
+   element present in the [n/2] index of the sorted array
+   is majority element i.e 1 where n is size of array.
+"""
+
+# function to find majority element
+def majority_element(array: list) -> int:
+    """
+    Return majority element in the list.
+    """
+    array.sort()
+    return array[len(array) // 2]
+
+
+if __name__ == "__main__":
+    import doctest
+    doctest.testmod()