diff --git "a/leetcode2/1easy/\354\265\234\354\233\220\354\244\200/Q3487.java" "b/leetcode2/1easy/\354\265\234\354\233\220\354\244\200/Q3487.java"
new file mode 100644
index 00000000..fbd1dab9
--- /dev/null
+++ "b/leetcode2/1easy/\354\265\234\354\233\220\354\244\200/Q3487.java"
@@ -0,0 +1,31 @@
+package Leetcode.최원준;
+
+/*
+1. 아이디어 :
+방문처리와, 최대값을 유지
+
+2. 시간복잡도 :
+O( n )
+
+3. 자료구조/알고리즘 :
+- / -
+ */
+
+import java.util.HashSet;
+import java.util.Set;
+
+public class Q3487 {
+    class Solution {
+        public int maxSum(int[] nums) {
+            Set<Integer> visited = new HashSet<>();
+            int ans = 0;
+            int cmax = Integer.MIN_VALUE;
+            for (int num : nums) {
+                if (!visited.contains(num) && num > 0) ans+=num;
+                visited.add(num);
+                cmax = Math.max(cmax, num);
+            }
+            return ans == 0? cmax : ans;
+        }
+    }
+}
diff --git "a/leetcode2/2medium/\354\265\234\354\233\220\354\244\200/Q911.java" "b/leetcode2/2medium/\354\265\234\354\233\220\354\244\200/Q911.java"
new file mode 100644
index 00000000..746fb0e8
--- /dev/null
+++ "b/leetcode2/2medium/\354\265\234\354\233\220\354\244\200/Q911.java"
@@ -0,0 +1,66 @@
+package Leetcode.최원준;
+
+/*
+1. 아이디어 :
+time에 따른 최고 투표자를 미리 계산합니다.
+q 메서드가 호출될떄마다 이분탐색으로 시간에 해당하는 인덱스를 찾고, 그 인덱스의 투표자를 리턴
+
+2. 시간복잡도 :
+O( n ) / O( log n ) * 호출횟수(m)
+
+3. 자료구조/알고리즘 :
+해시맵 / 이분탐색
+ */
+
+import java.util.HashMap;
+import java.util.Map;
+
+public class Q911 {
+    class TopVotedCandidate {
+        int n;
+        int[] times;
+        int[] rank;
+
+        public TopVotedCandidate(int[] persons, int[] times) {
+            this.n = persons.length;
+            this.times = times;
+            this.rank = new int[n];
+
+            Map<Integer, Integer> counter = new HashMap<>();
+            int cmax = 0;
+            int candid = -1;
+
+            for (int i=0; i<n; i++) {
+                int person = persons[i], time = times[i];
+                counter.put(person, counter.getOrDefault(person, 0)+1);
+
+                if (counter.get(person) >= cmax) { // >= 최근 반영
+                    cmax = counter.get(person);
+                    candid = person;
+                }
+                rank[i] = candid;
+            }
+        }
+
+        public int q(int t) {
+            int left = 0, right = n-1;
+
+            while (left <= right) {
+                int mid = left + (right-left)/2;
+                if (times[mid] <= t) {
+                    left = mid + 1;
+                } else {
+                    right = mid - 1;
+                }
+            }
+            return rank[right];
+
+        }
+    }
+
+/**
+ * Your TopVotedCandidate object will be instantiated and called as such:
+ * TopVotedCandidate obj = new TopVotedCandidate(persons, times);
+ * int param_1 = obj.q(t);
+ */
+}
diff --git "a/leetcode2/3hard/\354\265\234\354\233\220\354\244\200/Q1928.java" "b/leetcode2/3hard/\354\265\234\354\233\220\354\244\200/Q1928.java"
new file mode 100644
index 00000000..fed22048
--- /dev/null
+++ "b/leetcode2/3hard/\354\265\234\354\233\220\354\244\200/Q1928.java"
@@ -0,0 +1,66 @@
+package Leetcode;
+
+/*
+1. 아이디어 :
+다익스트라 사용
+
+2. 시간복잡도 :
+O( n * log n + m ) // n: 노드, m: 엣지
+
+3. 자료구조/알고리즘 :
+해시맵 / 다익스트라
+ */
+
+import java.util.*;
+
+public class Q1928 {
+    class Pair {
+        int node;
+        int time;
+        int fees;
+        public Pair(int node, int time, int fees) {
+            this.node=node;
+            this.time=time;
+            this.fees=fees;
+        }
+    }
+
+    class Solution {
+        public int minCost(int maxTime, int[][] edges, int[] passingFees) {
+            // n: nodes, m: edges
+            int n = passingFees.length;
+            Map<Integer, List<int[]>> graph = new HashMap<>();
+            for (int[] edge : edges) {  // m
+                int u = edge[0], v = edge[1], c = edge[2];
+                graph.putIfAbsent(u, new ArrayList<>());
+                graph.putIfAbsent(v, new ArrayList<>());
+                graph.get(u).add(new int[]{v, c});
+                graph.get(v).add(new int[]{u, c});
+            }
+
+            PriorityQueue<Pair> pq = new PriorityQueue<>((a, b) -> {
+                return a.fees - b.fees;
+            });
+            pq.add(new Pair(0,0,passingFees[0]));
+
+            int[][] dp = new int[n][maxTime+1]; // [x][y] = x노드에 y시간에 도착했을때, 최소 fees
+            for (int[] row : dp) Arrays.fill(row, Integer.MAX_VALUE);
+            dp[0][0] = passingFees[0];
+
+            while (!pq.isEmpty()) { // n
+                Pair curr = pq.poll(); // logn
+                int cnode = curr.node, ctime = curr.time, cfees = curr.fees;
+                if (dp[cnode][ctime] != cfees) continue;
+                if (cnode == n-1) return cfees;
+
+                for (int[] neighbor : graph.getOrDefault(cnode, new ArrayList<>())) { // m
+                    int nnode = neighbor[0], ntime = neighbor[1], nfees = passingFees[neighbor[0]];
+                    if (ctime + ntime > maxTime || dp[nnode][ctime + ntime] <= cfees + nfees) continue;
+                    dp[nnode][ctime+ntime] = cfees + nfees;
+                    pq.add(new Pair(nnode, ctime+ntime, cfees + nfees));
+                }
+            }
+            return -1;
+        }
+    }
+}