diff --git a/Problem1.java b/Problem1.java
index e69de29b..88664c54 100644
--- a/Problem1.java
+++ b/Problem1.java
@@ -0,0 +1,24 @@
+// TC: O(n)
+// SC: O(n)
+
+// 1: We use a HashMap with a key:value pair of the number from the input array: the index at which it is present
+// 2: For each element in the array, we determine whether the difference from the target is present in the array
+// 3: If the difference does not exist, we insert the current number into the array along with its index
+class Solution {
+    public int[] twoSum(int[] nums, int target) {
+
+        HashMap<Integer, Integer> map = new HashMap<>();
+
+        for(int i = 0; i<nums.length; i++){
+            int item = target - nums[i];
+            if(map.containsKey(item)){
+                return new int[]{i, map.get(item)};
+            }
+            else{
+                map.put(nums[i], i);
+            }
+        }
+        return new int[]{-1,-1};
+
+    }
+}
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