[hjeomdev] WEEK 01 solutions

contains-duplicate/hjeomdev.java

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+import java.util.HashSet;
+import java.util.Set;
+
+class Solution {
+    public boolean containsDuplicate(int[] nums) {
+        Set set = new HashSet();
+        for (int num : nums) {
+            set.add(num);
+        }
+
+        if (set.size() != nums.length) {
+            return true;
+        } else {
+            return false;
+        }
+    }
+}

top-k-frequent-elements/hjeomdev.java

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+class Solution {
+    public int[] topKFrequent(int[] nums, int k) {
+        Map<Integer, Integer> map = new HashMap<>();
+
+        for (int num : nums) {
+            int current = map.getOrDefault(num, 0);
+            map.put(num, current + 1);
+        }
+
+        List<Integer> keySet = new ArrayList<>(map.keySet());
+        keySet.sort((o1, o2) -> map.get(o2).compareTo(map.get(o1)));
+
+        return keySet.subList(0, k)
+                .stream()
+                .mapToInt(Integer::intValue)
+                .toArray();
+    }
+}

two-sum/hjeomdev.java

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+class Solution {
+    public int[] twoSum(int[] nums, int target) {
+        int[] answer = new int[2];
+        for (int i = 0; i < nums.length; i++) {
+            for (int j = i + 1; j < nums.length; j++) {
+                if (nums[i] + nums[j] == target) {
+                    answer[0] = i;
+                    answer[1] = j;
+                    break;
+                }
+            }
+        }
+        return answer;
+    }
+}