Create Longest Arithmetic Subarray.cpp

HacktoberFest2021/C++ Programs/Longest Arithmetic Subarray.cpp

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+#include <bits/stdc++.h>
+using namespace std;
+
+// Function to return the length
+// of longest subarray forming an AP
+int getMaxLength(int arr[], int N)
+{
+
+	// Minimum possible length of
+	// required subarray is 2
+	int res = 2;
+
+	// Stores the length of the
+	// current subarray
+	int dist = 2;
+
+	// Stores the common difference
+	// of the current AP
+	int curradj = (arr[1] - arr[0]);
+
+	// Stores the common difference
+	// of the previous AP
+	int prevadj = (arr[1] - arr[0]);
+	for (int i = 2; i < N; i++) {
+		curradj = arr[i] - arr[i - 1];
+
+		// If the common differences
+		// are found to be equal
+		if (curradj == prevadj) {
+
+			// Continue the previous subarray
+			dist++;
+		}
+
+		// Start a new subarray
+		else {
+			prevadj = curradj;
+
+			// Update the length to
+			// store maximum length
+			res = max(res, dist);
+			dist = 2;
+		}
+	}
+
+	// Update the length to
+	// store maximum length
+	res = max(res, dist);
+
+	// Return the length of
+	// the longest subarray
+	return res;
+}
+int main()
+{
+	int arr[] = { 10, 7, 4, 6, 8, 10, 11 };
+	int N = sizeof(arr) / sizeof(arr[0]);
+	cout << getMaxLength(arr, N);
+}