Two Sum II - Input Array Is Sorted

README.md

@@ -68,16 +68,17 @@ int sum(int[] A, int n) {
 
 ## Solutions
 
-| ID   | Difficulty | Problem                         | Topics                            | Link                                                       |
-|------|------------|---------------------------------|-----------------------------------|------------------------------------------------------------|
-| 0001 | Easy       | Two Sum                         | Array, HashMap                    | [solution](./docs/0001-Two-Sum.md)                         |
-| 0002 | Medium     | Add Two numbers                 | LinkedList, Recursion             |                                                            |
-| 0049 | Medium     | Group Anagrams                  | Array, HashTable, String, Sorting | [solution](./docs/0049-Group-Anagrams.md )                 |
-| 0121 | Easy       | Best Time to Buy and Sell Stock | Array                             | [solution](./docs/0121-Best-Time-to-Buy-and-Sell-Stock.md) |
-| 0125 | Easy       | Valid Palindrome                | String, Two Pointers              | [solution](./docs/0125-Valid-Palindrome.md)                |       
-| 0169 | Easy       | Majority Element                | Array, HashTable, Counting        | [solution](./docs/0169-Majority-Element.md)                |
-| 0217 | Easy       | Contains Duplicate              | Array                             | [solution](./docs/0217-Contains-Duplicate.md)              |
-| 0219 | Easy       | Contains Duplicate II           | Array                             | [solution](./docs/0219-Contains-Duplicate-II.md)           |
-| 0238 | Medium     | Product of Array Except Self    | Array                             | [solution](./docs/0238-Product-Of-Array-Except-Self.md)    |
-| 0242 | Easy       | Valid Anagram                   | String, HashTable                 | [solution](./docs/0242-Valid-Anagram.md)                   |   
-| 0347 | Medium     | Top K Frequent Elements         | Array, HashMap, Bucket Sort       | [Solution](./docs/0347-Top-K-Frequent-Elements.md)         |
+| ID   | Difficulty | Problem                            | Topics                            | Link                                                       |
+|------|------------|------------------------------------|-----------------------------------|------------------------------------------------------------|
+| 0001 | Easy       | Two Sum                            | Array, HashMap                    | [solution](./docs/0001-Two-Sum.md)                         |
+| 0002 | Medium     | Add Two numbers                    | LinkedList, Recursion             |                                                            |
+| 0049 | Medium     | Group Anagrams                     | Array, HashTable, String, Sorting | [solution](./docs/0049-Group-Anagrams.md )                 |
+| 0121 | Easy       | Best Time to Buy and Sell Stock    | Array                             | [solution](./docs/0121-Best-Time-to-Buy-and-Sell-Stock.md) |
+| 0125 | Easy       | Valid Palindrome                   | String, Two Pointers              | [solution](./docs/0125-Valid-Palindrome.md)                |       
+| 0167 | Medium     | Two Sum II - Input Array Is Sorted | Array, Two Pointers               | [solution](./docs/0167-Two-Sum-II-Array-Is-Sorted.md)      |
+| 0169 | Easy       | Majority Element                   | Array, HashTable, Counting        | [solution](./docs/0169-Majority-Element.md)                |
+| 0217 | Easy       | Contains Duplicate                 | Array                             | [solution](./docs/0217-Contains-Duplicate.md)              |
+| 0219 | Easy       | Contains Duplicate II              | Array                             | [solution](./docs/0219-Contains-Duplicate-II.md)           |
+| 0238 | Medium     | Product of Array Except Self       | Array                             | [solution](./docs/0238-Product-Of-Array-Except-Self.md)    |
+| 0242 | Easy       | Valid Anagram                      | String, HashTable                 | [solution](./docs/0242-Valid-Anagram.md)                   |   
+| 0347 | Medium     | Top K Frequent Elements            | Array, HashMap, Bucket Sort       | [Solution](./docs/0347-Top-K-Frequent-Elements.md)         |

docs/0167-Two-Sum-II-Array-Is-Sorted.md

@@ -0,0 +1,24 @@
+# [Two Sum II - Input Array Is Sorted](https://leetcode.com/problems/two-sum-ii-input-array-is-sorted/description/)
+
+## Intuition
+
+Given a sorted array, we need to find two numbers that sum up to a specific target. Since the array is sorted, we can use a two-pointer technique to find the two numbers efficiently. This approach leverages the sorted nature of the array to eliminate the need for nested loops, thus optimizing the search process.
+
+## Approach
+
+1. **Initialize Two Pointers:** Start with one pointer `leftIndex` at the beginning of the array and the other pointer `rightIndex` at the end of the array.
+2. **Iterate with Two Pointers:**
+    - Calculate the sum of the elements at the two pointers.
+    - If the sum is less than the target, move the `leftIndex` pointer to the right to increase the sum.
+    - If the sum is greater than the target, move the `rightIndex` pointer to the left to decrease the sum.
+    - If the sum equals the target, return the 1-indexed positions of the two elements.
+3. **Return Result:** If the loop exits without finding the target sum (which is guaranteed not to happen due to problem constraints), throw an `IllegalArgumentException.
+
+## Complexity
+
+- **Time Complexity: `O(N)`**, where `N` is the length of the array. Each element is checked at most once, making the time complexity linear.
+- **Time Complexity: `O(1)`**, as we are using only a constant amount of extra space for the pointers and a few variables.
+
+## Code
+
+- [Java](../src/main/java/io/dksifoua/leetcode/twosum2/Solution.java)

src/main/java/io/dksifoua/leetcode/twosum2/Solution.java

@@ -0,0 +1,20 @@
+package io.dksifoua.leetcode.twosum2;
+
+public class Solution {
+
+    public int[] twoSum(int[] numbers, int target) {
+        int leftIndex = 0, rightIndex = numbers.length - 1;
+        while (leftIndex < rightIndex) {
+            int sum = numbers[leftIndex] + numbers[rightIndex];
+            if (sum < target) {
+                leftIndex += 1;
+            } else if (sum > target) {
+                rightIndex -= 1;
+            } else {
+                return new int[] { leftIndex + 1, rightIndex + 1 };
+            }
+        }
+
+        throw new IllegalArgumentException();
+    }
+}

src/test/java/io/dksifoua/leetcode/twosum2/SolutionTest.java

@@ -0,0 +1,30 @@
+package io.dksifoua.leetcode.twosum2;
+
+import org.junit.jupiter.api.Assertions;
+import org.junit.jupiter.api.Test;
+
+public class SolutionTest {
+
+    public final Solution solution = new Solution();
+
+    @Test
+    void test1() {
+        int[] expected = { 1, 2 };
+        int[] actual = solution.twoSum(new int[] { 2, 7, 11, 15 }, 9);
+        Assertions.assertArrayEquals(expected, actual);
+    }
+
+    @Test
+    void test2() {
+        int[] expected = { 1, 3 };
+        int[] actual = solution.twoSum(new int[] { 2, 3, 4 }, 6);
+        Assertions.assertArrayEquals(expected, actual);
+    }
+
+    @Test
+    void test3() {
+        int[] expected = { 1, 2 };
+        int[] actual = solution.twoSum(new int[] { -1, 0 }, -1);
+        Assertions.assertArrayEquals(expected, actual);
+    }
+}