solution two sum

Author: river20s

two-sum/river20s.java

@@ -0,0 +1,24 @@
+/*
+ * T.C: O(n) -> 배열 nums를 한 번 순회
+ * S.C: O(n) → 최대 n개의 요소가 저장됨
+ */
+import java.util.HashMap;
+
+class Solution {
+    public int[] twoSum(int[] nums, int target) {
+
+        HashMap<Integer, Integer> map = new HashMap<>();
+        for  (int i = 0; i < nums.length; i++) {
+            int k = target - nums[i];
+
+            if (map.containsKey(k)) {
+                return new int[] { map.get(k), i };
+            }
+
+            map.put(nums[i], i);
+        }
+        throw new IllegalArgumentException("exception handling for java compilation");
+        
+    }
+}
+