create: solution of two sum

Week_01/TwoSum.java

@@ -0,0 +1,34 @@
+import java.util.HashMap;
+import java.util.Map;
+
+public class TwoSum {
+    /**
+     * The Brute Force Solution
+     *
+     */
+    public int[] twoSumBruteForce(int[] nums, int target) {
+        for (int i = 0; i < nums.length; i++) {
+            for (int j = i + 1; j < nums.length; j++) {
+                if (nums[j] == target - nums[i]) {
+                    return new int[]{i, j};
+                }
+            }
+        }
+        throw new IllegalArgumentException("No two sum solution");
+    }
+
+    /**
+     * The Solution By Hash Table
+     *
+     */
+    public int[] twoSumHashTable(int[] nums, int target) {
+        Map<Integer, Integer> map = new HashMap<>();
+        for (int i = 0; i < nums.length; i++) {
+            if (map.containsKey(target - nums[i])) {
+                return new int[]{map.get(target - nums[i]), i};
+            }
+            map.put(nums[i], i);
+        }
+        throw new IllegalArgumentException("No two sum solution");
+    }
+}