two sum java

Java/two-sum.java

@@ -0,0 +1,29 @@
+/**
+* One-pass Hash Table
+* we iterate and inserting elements into the table, 
+* we also look back to check if current element's complement already exists in the table. 
+* If it exists, we have found a solution and return immediately.
+*
+* Time complexity : O(n)
+* Space complexity : O(n)
+*/
+class Solution {
+    public int[] twoSum(int[] nums, int target) {
+
+        Map<Integer, Integer> sumMap = new HashMap<>();
+        int [] result = new int[2];
+
+        for (int i=0; i<nums.length(); i++){
+
+            if(!sumMap.isEmpty() && sumMap.containsKey(nums[i])){
+                result[0] = sumMap.get(nums[i]);
+                result[1] = i;
+
+                return result;
+            }
+            else{
+                sumMap.put(target-nums[i],i);
+            }
+        }
+    }
+}