TwoPointers.java

packagecom.thealgorithms.others;

/**
 * The two-pointer technique is a useful tool to utilize when searching for
 * pairs in a sorted array.
 *
 * <p>
 * Link: https://www.geeksforgeeks.org/two-pointers-technique/
 */
finalclassTwoPointers {
privateTwoPointers() {
 }

/**
 * Given a sorted array arr (sorted in ascending order), find if there exists
 * any pair of elements such that their sum is equal to the key.
 *
 * @param arr the array containing elements (must be sorted in ascending order)
 * @param key the number to search
 * @return {@code true} if there exists a pair of elements, {@code false} otherwise.
 */
publicstaticbooleanisPairedSum(int[] arr, intkey) {
inti = 0; // index of the first element
intj = arr.length - 1; // index of the last element

while (i < j) {
intsum = arr[i] + arr[j];
if (sum == key) {
returntrue;
 } elseif (sum < key) {
i++;
 } else {
j--;
 }
 }
returnfalse;
 }
}