Merge pull request TheAlgorithms#1467 from varunvjha/varun-patch

Added Two Pointers Algorithm

Author: realDuYuanChao

Others/TwoPointers.java

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