diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..37b1922
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1,2 @@
+/.idea/
+/out/
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diff --git a/out/production/leetcode/com/leetcode/TopVotedCandidate.class b/out/production/leetcode/com/leetcode/TopVotedCandidate.class
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diff --git a/out/production/leetcode/com/leetcode/TreeNode.class b/out/production/leetcode/com/leetcode/TreeNode.class
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diff --git a/src/main/java/com/leetcode/1155.java b/src/main/java/com/leetcode/1155.java
new file mode 100644
index 0000000..2e9e955
--- /dev/null
+++ b/src/main/java/com/leetcode/1155.java
@@ -0,0 +1,28 @@
+package com.leetcode;
+
+class Solution1155 {
+    public int numRollsToTarget(int n, int k, int target) {
+        long MAX = 1000000007;
+        long[] dp = new long[target + 1];
+        for (int i = 1; i <= k && i < dp.length; i++) {
+            dp[i] = 1;
+        }
+        for (int i = 1; i < n; i++) {
+            for (int j = dp.length-1; j > 0; j--) {
+                dp[j] = 0;
+                for (int t = 1; t <= k; t++) {
+                    if (j - t <= 0) {
+                        break;
+                    }
+                    dp[j] = (dp[j - t] + dp[j]) % MAX;
+                }
+            }
+        }
+        return (int)dp[target];
+    }
+
+    public static void main(String[] args) {
+        Solution1155 so = new Solution1155();
+        System.out.println(so.numRollsToTarget(4, 6, 7));
+    }
+}
\ No newline at end of file
diff --git a/src/main/java/com/leetcode/2034.java b/src/main/java/com/leetcode/2034.java
new file mode 100644
index 0000000..922da2f
--- /dev/null
+++ b/src/main/java/com/leetcode/2034.java
@@ -0,0 +1,71 @@
+package com.leetcode;
+
+import javafx.util.Pair;
+
+import java.util.*;
+
+class StockPrice {
+    HashMap<Integer, Integer> map;
+    Queue<Pair<Integer, Integer>> maxQ;
+    Queue<Pair<Integer, Integer>> minQ;
+    int curTimestamp;
+
+    public StockPrice() {
+        this.map = new HashMap<>();
+        this.minQ = new PriorityQueue<>(
+                (o1, o2) -> -o2.getValue().compareTo(o1.getValue())
+        );
+        this.maxQ = new PriorityQueue<>(
+                (o1, o2) -> o2.getValue().compareTo(o1.getValue())
+        );
+        this.curTimestamp = 0;
+    }
+
+    public void update(int timestamp, int price) {
+        if (timestamp > this.curTimestamp) {
+            this.curTimestamp = timestamp;
+        }
+        this.map.put(timestamp, price);
+        this.maxQ.add(new Pair<>(timestamp, price));
+        this.minQ.add(new Pair<>(timestamp, price));
+    }
+
+    public int current() {
+        return this.map.get(this.curTimestamp);
+    }
+
+    public int maximum() {
+        while(true) {
+            Pair<Integer, Integer> peek = this.maxQ.peek();
+            if (peek == null) {
+                return -1;
+            }
+            if (Objects.equals(peek.getValue(), this.map.get(peek.getKey()))) {
+                return peek.getValue();
+            } else {
+                this.maxQ.remove();
+            }
+        }
+    }
+
+    public int minimum() {
+        while(true) {
+            Pair<Integer, Integer> peek = this.minQ.peek();
+            if (peek == null) {
+                return -1;
+            }
+            if (Objects.equals(peek.getValue(), this.map.get(peek.getKey()))) {
+                return peek.getValue();
+            } else {
+                this.minQ.remove();
+            }
+        }
+    }
+
+    public static void main(String[] args) {
+        StockPrice obj = new StockPrice();
+        obj.update(3, 9651);
+        obj.update(3, 6897);
+        System.out.println(obj.maximum());
+    }
+}
diff --git a/src/main/java/com/leetcode/2103.java b/src/main/java/com/leetcode/2103.java
new file mode 100644
index 0000000..bbcea80
--- /dev/null
+++ b/src/main/java/com/leetcode/2103.java
@@ -0,0 +1,24 @@
+package com.leetcode;
+
+import java.util.ArrayList;
+import java.util.HashSet;
+
+class Solution2103 {
+    public int countPoints(String rings) {
+        ArrayList<HashSet<Integer>> maps = new ArrayList<>();
+        for (int i = 0; i < 10; i++) {
+            maps.add(new HashSet<>());
+        }
+        for (int i = 0; 2 * i < rings.length(); i++) {
+            int color = rings.charAt(2*i), idx = rings.charAt(2*i+1)-'0';
+            maps.get(idx).add(color);
+        }
+        int res = 0;
+        for (HashSet<Integer> map: maps) {
+            if (map.size() >= 3) {
+                res++;
+            }
+        }
+        return res;
+    }
+}
\ No newline at end of file
diff --git a/src/main/java/com/leetcode/2512.java b/src/main/java/com/leetcode/2512.java
new file mode 100644
index 0000000..200ca4d
--- /dev/null
+++ b/src/main/java/com/leetcode/2512.java
@@ -0,0 +1,38 @@
+package com.leetcode;
+
+import java.util.*;
+import java.util.stream.Collectors;
+
+class Solution2512 {
+    public List<Integer> topStudents(String[] positive_feedback, String[] negative_feedback, String[] report, int[] student_id, int k) {
+        HashSet<String> pos = new HashSet<>(Arrays.asList(positive_feedback));
+        HashSet<String> neg = new HashSet<>(Arrays.asList(negative_feedback));
+        HashMap<Integer, Integer> scores = new HashMap<>();
+        for (int i = 0; i < report.length; i++) {
+            String[] ss = report[i].split(" ");
+            int score = 0;
+            for (String s: ss) {
+                if (pos.contains(s)) {
+                    score += 3;
+                }
+                if (neg.contains(s)) {
+                    score -= 1;
+                }
+            }
+            scores.put(student_id[i], score);
+        }
+        List<Integer> res = Arrays.stream(student_id).boxed().collect(Collectors.toList());
+        Collections.sort(res, new Comparator<Integer>() {
+            @Override
+            public int compare(Integer o1, Integer o2) {
+                Integer score1 = scores.get(o1);
+                Integer score2 = scores.get(o2);
+                if (Objects.equals(score1, score2)) {
+                    return o1.compareTo(o2);
+                }
+                return -score1.compareTo(score2);
+            }
+        });
+        return res.subList(0, k);
+    }
+}
\ No newline at end of file
diff --git a/src/main/java/com/leetcode/2530.java b/src/main/java/com/leetcode/2530.java
new file mode 100644
index 0000000..9b4870e
--- /dev/null
+++ b/src/main/java/com/leetcode/2530.java
@@ -0,0 +1,25 @@
+package com.leetcode;
+
+import java.util.PriorityQueue;
+
+class Solution2530 {
+    public long maxKelements(int[] nums, int k) {
+        PriorityQueue<Integer> q = new PriorityQueue<>((o1, o2) -> {return -o1.compareTo(o2);});
+        long s = 0;
+        for (int num: nums) {
+            q.add(num);
+        }
+        for (int i = 0; i < k; i++) {
+            long peek = q.remove();
+            s += peek;
+            peek = (peek + 2) / 3;
+            q.add((int) peek);
+        }
+        return s;
+    }
+
+    public static void main(String[] args) {
+        Solution2530 solution2530 = new Solution2530();
+        System.out.println(solution2530.maxKelements(new int[]{10,10,10,10,10}, 5));
+    }
+}
\ No newline at end of file
diff --git a/src/main/java/com/leetcode/2578.java b/src/main/java/com/leetcode/2578.java
new file mode 100644
index 0000000..420bc19
--- /dev/null
+++ b/src/main/java/com/leetcode/2578.java
@@ -0,0 +1,31 @@
+package com.leetcode;
+
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.Collections;
+import java.util.List;
+
+class Solution2578 {
+    public int splitNum(int num) {
+        ArrayList<Integer> nums = new ArrayList<>();
+        while (num > 0) {
+            nums.add(num % 10);
+            num /= 10;
+        }
+        Collections.sort(nums);
+        int v1 = 0, v2 = 0;
+        for (int k = 0; k < nums.size(); k++) {
+            if (k % 2 == 0) {
+                v1 = v1 * 10 + nums.get(k);
+            } else {
+                v2 = v2 * 10 + nums.get(k);
+            }
+        }
+        return v1 + v2;
+    }
+
+    public static void main(String[] args) {
+        Solution2578 so = new Solution2578();
+        System.out.println(so.splitNum(4325));
+    }
+}
\ No newline at end of file
diff --git a/src/main/java/com/leetcode/2678.java b/src/main/java/com/leetcode/2678.java
new file mode 100644
index 0000000..b0c2155
--- /dev/null
+++ b/src/main/java/com/leetcode/2678.java
@@ -0,0 +1,13 @@
+package com.leetcode;
+
+class Solution2678 {
+    public int countSeniors(String[] details) {
+        int res = 0;
+        for (String detail: details) {
+            if (Integer.parseInt(detail.substring(11, 13)) > 60) {
+                res++;
+            }
+        }
+        return res;
+    }
+}
\ No newline at end of file
diff --git a/src/main/java/com/leetcode/2698.java b/src/main/java/com/leetcode/2698.java
new file mode 100644
index 0000000..a08ebdb
--- /dev/null
+++ b/src/main/java/com/leetcode/2698.java
@@ -0,0 +1,25 @@
+package com.leetcode;
+
+class Solution2698 {
+    public int punishmentNumber(int n) {
+        int sum = 0;
+        for (int i = 1; i <= n; i++) {
+            int v = i * i;
+            if (bfs(v, i)) {
+                sum += v;
+            }
+        }
+        return sum;
+    }
+
+    private boolean bfs (int v, int target) {
+        for (int i = 10; v / i > 0; i *= 10) {
+            int r = v % i;
+            int l = v / i;
+            if (target - r > 0 && bfs(l, target - r)) {
+                return true;
+            }
+        }
+        return v == target;
+    }
+}
\ No newline at end of file
diff --git a/src/main/java/com/leetcode/274.java b/src/main/java/com/leetcode/274.java
new file mode 100644
index 0000000..3039ff3
--- /dev/null
+++ b/src/main/java/com/leetcode/274.java
@@ -0,0 +1,25 @@
+package com.leetcode;
+
+import java.util.Arrays;
+
+class Solution274 {
+    public int hIndex(int[] citations) {
+        int l = 0, r = 1000;
+        while (l < r) {
+            int mid = (l + r + 1) / 2;
+
+            int cnt = 0;
+            for (int c: citations) {
+                if (c >= mid) {
+                    cnt++;
+                }
+            }
+            if (cnt >= mid) {
+                l = mid;
+            } else {
+                r = mid - 1;
+            }
+        }
+        return l;
+    }
+}
\ No newline at end of file
diff --git a/src/main/java/com/leetcode/275.java b/src/main/java/com/leetcode/275.java
new file mode 100644
index 0000000..4509bd6
--- /dev/null
+++ b/src/main/java/com/leetcode/275.java
@@ -0,0 +1,12 @@
+package com.leetcode;
+
+class Solution275 {
+    public int hIndex(int[] citations) {
+        for (int i = citations.length-1; i >= 0; i--) {
+            if (citations[i] < citations.length - i) {
+                return citations.length - i - 1;
+            }
+        }
+        return citations.length;
+    }
+}
\ No newline at end of file