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Author: samcho0608

contains-duplicate/samcho0608.java

@@ -1,12 +1,18 @@
 import java.util.HashSet;
 
+// link: https://leetcode.com/problems/contains-duplicate/description/
+// difficulty: Easy
 class Solution {
-    // return: does any value appear more than once in the array
-    // Time Complexity: O(n)
-    // Space Complexity: O(n)
+    // Problem:
+    // * return: does any value appear more than once in the array
+    // Solution:
+    // * Time Complexity: O(N)
+    // * Space Complexity: O(N)
     public boolean containsDuplicate(int[] nums) {
+        // Space Complexity: O(N)
         HashSet<Integer> uniqNums = new HashSet<>();
 
+        // Time Complexity: O(N)
         for(int num : nums) {
             if(!uniqNums.add(num)) return true;
         }

house-robber/samcho0608.java

@@ -1,3 +1,5 @@
+// link: https://leetcode.com/problems/house-robber/description/
+// difficulty: Medium
 class Solution {
     // Problem:
     // * can't rob two adj houses in the same night

longest-consecutive-sequence/samcho0608.java

@@ -1,6 +1,8 @@
 import java.util.HashSet;
 import java.util.Set;
 
+// link: https://leetcode.com/problems/longest-consecutive-sequence/
+// difficulty: Medium
 class Solution {
     // Problem: 
     // * nums is unsorted

top-k-frequent-elements/samcho0608.java

@@ -1,5 +1,8 @@
 import java.util.*;
 
+// link: https://leetcode.com/problems/top-k-frequent-elements/description/
+// difficulty: Medium
+
 // Time complexity: O(Nlogk)
 // Space complexity: O(N)
 class Solution1 {

two-sum/samcho0608.java

@@ -1,25 +1,33 @@
 import java.util.HashMap;
 import java.util.Map;
 
+// link: https://leetcode.com/problems/two-sum/description/
+// difficulty: Easy
 class Solution {
-    // return: indices of two numbers that add up to `target`
+    // Problem
     // * exactly one solution
     // * must use index only once
-
-    // Time Complexity: O(n)
-    // Space Complexity: O(n)
+    // * return: indices of two numbers that add up to `target`
+    // Solution:
+    // * Time Complexity: O(N)
+    // * Space Complexity: O(N)
     public int[] twoSum(int[] nums, int target) {
+        // Space Complexity: O(N)
         Map<Integer, Integer> indexByNum = new HashMap<>();
 
+        // Time Complexity: O(N)
         for(int i = 0; i < nums.length; i++) {
             int numI = nums[i];
             indexByNum.put(numI, i);
         }
 
+        // Time Complexity: O(N)
         for(int i = 0; i < nums.length; i++) {
             int numI = nums[i];
             Integer compl = indexByNum.getOrDefault(target-numI, null);
-            if(compl != null && i != compl) return new int[] {i, compl};
+
+            if(compl != null && i != compl)
+                return new int[] {i, compl};
         }
 
         return null;