1. Two Sum

Author: TonyKim9401

two-sum/TonyKim9401.java

@@ -0,0 +1,15 @@
+class Solution {
+    public int[] twoSum(int[] nums, int target) {
+        // time complexity: O(n);
+        // space complexity: O(n);
+        Map<Integer, Integer> map = new HashMap<>();
+        for (int i = 0; i < nums.length; i++) map.put(nums[i], i);
+
+        for (int i = 0; i < nums.length; i++) {
+            int candidateKey = target - nums[i];
+            if (map.containsKey(candidateKey) && i != map.get(candidateKey))
+                return new int[]{i, map.get(candidateKey)};
+        }
+        return new int[]{-1, -1};
+    }
+}