add solution of two-sum

Author: Ujoonnee

two-sum/Ujoonnee.java

@@ -0,0 +1,13 @@
+class Solution {
+    public int[] twoSum(int[] nums, int target) {
+        for (int i=0; i<nums.length-1; i++) {
+            for(int j=i+1; j<nums.length; j++) {
+                if (nums[i] + nums[j] == target) {
+                    return new int[] { i, j };
+                }
+            }
+        }
+
+        return new int[] {};
+    }
+}