[Google] Arithmetic Progression Triplet

Question

link

Given a sorted set, find if there exist three elements in Arithmetic Progression or not.

Solution

This is a rather simple Arithmetic Progression question.

To find the three elements, we first fix an element as middle element and search for other two (one smaller and one greater).

O(n^2) time.

Code

written by me

public boolean longest(int[] A) {
	int len = A.length;
	for (int i = 1; i < len - 1; i++) {
		int left = i - 1;
		int right = i + 1;
		while (left >= 0 && right < len) {
			int total = A[left] + A[right];
			if (total > 2 * A[i]) {
				left--;
			} else if (total < 2 * A[i]) {
				right++;
			} else {
				return true;
			}
		}
	}
	return false;
}