Boyer Moore majority vote Algorithm in c++

C-Plus-Plus/README.md

@@ -191,3 +191,4 @@ _add list here_
 - [Kth smallest element](other/Kth_smallest_element.cpp)
 - [Generate all Subsets](other/subsets.cpp)
 - [Stock Span Problem](other/Stock_span_problem.cpp)
+- [Boyer–Moore majority vote algorithm](other/majority_vote_algorithm.cpp)

C-Plus-Plus/other/majority_vote_algorithm.cpp

@@ -0,0 +1,59 @@
+// The Boyer–Moore majority vote algorithm in C++
+// This algorithm finds a majority element, if there is one: i.e, an element that occurs repeatedly for more than half of the elements of the input.
+
+#include <bits/stdc++.h>
+using namespace std;
+
+// To find majority element
+int majority(int arr[], int arrsize) {
+	int index = 0, count = 1;
+	// finding num to check majority
+	for (int i = 1; i < arrsize; i++) {
+		if (arr[index] == arr[i])
+			count++;
+		else
+			count--;
+		if (count == 0) {
+			index = i;
+			count = 1;
+		}
+	}
+	int num = arr[index];
+	for (int i = 0; i < arrsize; i++)
+		if (arr[i] == num)
+			count++;
+	// checking for majority
+	if (count > arrsize / 2)
+		return num;
+	else
+		return -1;
+}
+
+int main() {
+	int n;
+	cout << "Enter no of elements:";
+	cin >> n;
+	cout << "\nEnter elements: ";
+	int arr[n];
+	for (int i = 0; i < n; i++)
+		cin >> arr[i];
+	int result = majority(arr, n);
+	if (result != -1)
+		cout << "Majority of a sequence is " << result << endl;
+	else
+		cout << "There is no majority \n";
+	return 0;
+}
+
+/*input/output:
+ Enter no of elements:5
+ Enter elements: 1 1 1 1 2
+ Majority of arr sequence is 1
+
+ Enter no of elements:5
+ Enter elements: 1 2 3 2 4
+ There is no Majority.
+
+ Time complexity : O(n)
+ Space complexity: O(1)
+ */