SumOfPairs.java

package javacodes;

/**
 * Given an array of integers A and an int m, find out if there exists a pair of
 * elements in A that add up to m in a relatively fast way.
 */
public class SumOfPairs {

    public static boolean sumExists(int[] list, int m) {
        int[] differences = new int[list.length];

        for (int i = 0; i < list.length; i++) {
            int curr = list[i];

            // ignore the trivial case where m is an element of the list.
            if (curr == m) {
                continue;
            }

            int diff = m - curr;

            for (int j = 0; j <= i; j++) {
                int currDiff = differences[j];

                if (currDiff == diff || currDiff == curr) {

                    System.out.println("A pair is " + curr + " and " + diff + "\n");
                    return true;
                }
            }

            differences[i] = diff;
        }

        return false;
    }

    public static void main(String[] args) {
        int[] l = {1, 8, 10, 3, 2, 6};

        System.out.println(sumExists(l, 8));
    }
}