From 5ed25890f133524d2ec093593322d2c4814ec356 Mon Sep 17 00:00:00 2001
From: s0___0k <61587396+s0ooo0k@users.noreply.github.com>
Date: Thu, 24 Jul 2025 00:12:30 +0900
Subject: [PATCH 1/4] Add two sum solution - s0ooo0k

---
 two-sum/s0ooo0k.java | 48 ++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 48 insertions(+)
 create mode 100644 two-sum/s0ooo0k.java

diff --git a/two-sum/s0ooo0k.java b/two-sum/s0ooo0k.java
new file mode 100644
index 000000000..444765ce1
--- /dev/null
+++ b/two-sum/s0ooo0k.java
@@ -0,0 +1,48 @@
+import java.util.Map;
+
+class Solution {
+
+    /*
+     * 시간복잡ㄷ도 개선
+     * 
+     * 시간복잡도 O(n)
+     * 공간복잡도 O(n)
+     */
+    public int[] twoSum(int[] nums, int target) {
+        Map<Integer, Integer> arr = new HashMap<>();
+
+        for(int i=0; i<nums.length; i++) {
+            if(arr.containsKey(target-nums[i])) {
+                return new int[]{arr.get(target-nums[i]), i};
+            }
+            arr.put(nums[i], i);
+        }
+        return new int[]{0, 0};
+    }
+    
+    
+    
+    /*
+     * 기존 풀이
+     * 
+     * 시간복잡도 O(n^2)
+     * 공간복잡도 O(1)
+     */
+
+    /*
+    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;
+                    return answer;
+                }
+            }
+        }
+        return answer;
+    }
+    */
+    
+}
\ No newline at end of file

From 78edcfe03bb2bb95b285268084956f64803f5e11 Mon Sep 17 00:00:00 2001
From: s0___0k <61587396+s0ooo0k@users.noreply.github.com>
Date: Thu, 24 Jul 2025 00:17:08 +0900
Subject: [PATCH 2/4] Fix two sum solution - s0ooo0k

---
 two-sum/s0ooo0k.java | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/two-sum/s0ooo0k.java b/two-sum/s0ooo0k.java
index 444765ce1..6e393fc53 100644
--- a/two-sum/s0ooo0k.java
+++ b/two-sum/s0ooo0k.java
@@ -44,5 +44,5 @@ public int[] twoSum(int[] nums, int target) {
         return answer;
     }
     */
-    
-}
\ No newline at end of file
+}
+

From ff72247168063b59442d7c7b6e42af8cdb92e0bd Mon Sep 17 00:00:00 2001
From: s0___0k <61587396+s0ooo0k@users.noreply.github.com>
Date: Fri, 25 Jul 2025 14:30:07 +0900
Subject: [PATCH 3/4] Add contains-duplicate solution - s0ooo0k

---
 contains-duplicate/s0ooo0k.java | 17 +++++++++++++++++
 1 file changed, 17 insertions(+)
 create mode 100644 contains-duplicate/s0ooo0k.java

diff --git a/contains-duplicate/s0ooo0k.java b/contains-duplicate/s0ooo0k.java
new file mode 100644
index 000000000..a81d2c619
--- /dev/null
+++ b/contains-duplicate/s0ooo0k.java
@@ -0,0 +1,17 @@
+/*
+ * 시간복잡도 O(n)
+ * 공간복잡도 O(n)
+ */
+class Solution {
+    public boolean containsDuplicate(int[] nums) {
+        Set<Integer> set = new HashSet<>();
+
+        for(int n : nums) {
+            if(set.contains(n)){
+                return true;
+            }
+            set.add(n);
+        }
+        return false;
+    }
+}
\ No newline at end of file

From 9e7950fd37e8a4b159de675511e159041cbd42fb Mon Sep 17 00:00:00 2001
From: s0___0k <61587396+s0ooo0k@users.noreply.github.com>
Date: Fri, 25 Jul 2025 14:30:22 +0900
Subject: [PATCH 4/4] Add contains-duplicate solution - s0ooo0k

---
 contains-duplicate/s0ooo0k.java | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/contains-duplicate/s0ooo0k.java b/contains-duplicate/s0ooo0k.java
index a81d2c619..5b0dd8c37 100644
--- a/contains-duplicate/s0ooo0k.java
+++ b/contains-duplicate/s0ooo0k.java
@@ -14,4 +14,6 @@ public boolean containsDuplicate(int[] nums) {
         }
         return false;
     }
-}
\ No newline at end of file
+}
+
+