50 lines
1.4 KiB
Java
50 lines
1.4 KiB
Java
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package Others;
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import java.util.Arrays;
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/**
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* The two pointer technique is a useful tool to utilize when searching for pairs in a sorted array.
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* <p>
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* link: https://www.geeksforgeeks.org/two-pointers-technique/
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*/
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class TwoPointers {
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public static void main(String[] args) {
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int[] arr = {10, 20, 35, 50, 75, 80};
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int key = 70;
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assert isPairedSum(arr, key); /* 20 + 60 == 70 */
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arr = new int[]{1, 2, 3, 4, 5, 6, 7};
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key = 13;
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assert isPairedSum(arr, key); /* 6 + 7 == 13 */
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key = 14;
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assert !isPairedSum(arr, key);
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}
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/**
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* Given a sorted array arr (sorted in ascending order).
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* Find if there exists any pair of elements such that their sum is equal to key.
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*
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* @param arr the array contains elements
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* @param key the number to search
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* @return {@code true} if there exists a pair of elements, {@code false} otherwise.
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*/
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private static boolean isPairedSum(int[] arr, int key) {
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/* array sorting is necessary for this algorithm to function correctly */
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Arrays.sort(arr);
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int i = 0; /* index of first element */
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int j = arr.length - 1; /* index of last element */
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while (i < j) {
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if (arr[i] + arr[j] == key) {
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return true;
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} else if (arr[i] + arr[j] < key) {
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i++;
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} else {
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j--;
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}
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}
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return false;
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}
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}
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