Update 0001-two-sum.java

Author: sanajitjana

Easy/0001-two-sum.java

@@ -1 +1,27 @@
+/**
+ * Problem: 1. Two Sum
+ * Difficulty: Easy
+ * URL: https://leetcode.com/problems/two-sum/
+ * 
+ * Approach:
+ * - Use a HashMap to store visited numbers and their indices.
+ * - Check if target - current exists in map.
+ * 
+ * Time Complexity: O(n)
+ * Space Complexity: O(n)
+ */
+
+class Solution {
+    public int[] twoSum(int[] nums, int target) {
+        Map<Integer, Integer> map = new HashMap<>();
+        for (int i = 0; i < nums.length; i++) {
+            int complement = target - nums[i];
+            if (map.containsKey(complement)) {
+                return new int[] { map.get(complement), i };
+            }
+            map.put(nums[i], i);
+        }
+        return new int[] {};
+    }
+}