[toychip] WEEK 01 solutions

contains-duplicate/toychip.java

@@ -0,0 +1,16 @@
+import java.util.HashSet;
+import java.util.Set;
+
+class Solution {
+    public boolean containsDuplicate(int[] nums) {
+        Set<Integer> answer = new HashSet<>();
+        for (int num : nums) {
+            if (!answer.contains(num)) {
+                answer.add(num);
+            } else {
+                return true;
+            }
+        }
+        return false;
+    }
+}

two-sum/toychip.java

@@ -0,0 +1,12 @@
+class Solution {
+    public int[] twoSum(int[] nums, int target) {
+        for (int i = 0; i < nums.length; i++) {
+            for (int j = i + 1; j < nums.length; j++) {
+                if (nums[i] + nums[j] == target) {
+                    return new int[]{i, j};
+                }
+            }
+        }
+        return null;
+    }
+}