Added tasks 3806-3828

Author: ThanhNIT

src/main/java/g3801_3900/s3806_maximum_bitwise_and_after_increment_operations/Solution.java

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+package g3801_3900.s3806_maximum_bitwise_and_after_increment_operations;
+
+// #Hard #Array #Sorting #Greedy #Bit_Manipulation #Senior_Staff #Weekly_Contest_484
+// #2026_06_09_Time_107_ms_(78.72%)_Space_51.33_MB_(44.68%)
+
+import java.util.Arrays;
+
+public class Solution {
+    public int maximumAND(int[] a, int b, int c) {
+        long e = 0;
+        int f = a.length;
+        long[] g = new long[f];
+        for (int h = 30; h >= 0; --h) {
+            long i = e | (1L << h);
+            for (int j = 0; j < f; ++j) {
+                long k = a[j];
+                long l = i & ~k;
+                if (l == 0) {
+                    g[j] = 0;
+                } else {
+                    int n = 63 - Long.numberOfLeadingZeros(l);
+                    while (((k >> n) & 1) == 1) {
+                        n++;
+                    }
+                    long o = (1L << n) - 1;
+                    g[j] = ((k & ~o) | (1L << n) | (i & o)) - k;
+                }
+            }
+            Arrays.sort(g);
+            long p = 0;
+            for (int q = 0; q < c; ++q) {
+                p += g[q];
+            }
+            if (p <= b) {
+                e = i;
+            }
+        }
+        return (int) e;
+    }
+}

src/main/java/g3801_3900/s3806_maximum_bitwise_and_after_increment_operations/readme.md

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+3806\. Maximum Bitwise AND After Increment Operations
+
+Hard
+
+You are given an integer array `nums` and two integers `k` and `m`.
+
+You may perform **at most** `k` operations. In one operation, you may choose any index `i` and **increase** `nums[i]` by 1.
+
+Return an integer denoting the **maximum** possible **bitwise AND** of any **subset** of size `m` after performing up to `k` operations optimally.
+
+**Example 1:**
+
+**Input:** nums = [3,1,2], k = 8, m = 2
+
+**Output:** 6
+
+**Explanation:**
+
+*   We need a subset of size `m = 2`. Choose indices `[0, 2]`.
+*   Increase `nums[0] = 3` to 6 using 3 operations, and increase `nums[2] = 2` to 6 using 4 operations.
+*   The total number of operations used is 7, which is not greater than `k = 8`.
+*   The two chosen values become `[6, 6]`, and their bitwise AND is `6`, which is the maximum possible.
+
+**Example 2:**
+
+**Input:** nums = [1,2,8,4], k = 7, m = 3
+
+**Output:** 4
+
+**Explanation:**
+
+*   We need a subset of size `m = 3`. Choose indices `[0, 1, 3]`.
+*   Increase `nums[0] = 1` to 4 using 3 operations, increase `nums[1] = 2` to 4 using 2 operations, and keep `nums[3] = 4`.
+*   The total number of operations used is 5, which is not greater than `k = 7`.
+*   The three chosen values become `[4, 4, 4]`, and their bitwise AND is 4, which is the maximum possible.
+
+**Example 3:**
+
+**Input:** nums = [1,1], k = 3, m = 2
+
+**Output:** 2
+
+**Explanation:**
+
+*   We need a subset of size `m = 2`. Choose indices `[0, 1]`.
+*   Increase both values from 1 to 2 using 1 operation each.
+*   The total number of operations used is 2, which is not greater than `k = 3`.
+*   The two chosen values become `[2, 2]`, and their bitwise AND is 2, which is the maximum possible.
+
+**Constraints:**
+
+*   <code>1 <= n == nums.length <= 5 * 10<sup>4</sup></code>
+*   <code>1 <= nums[i] <= 10<sup>9</sup></code>
+*   <code>1 <= k <= 10<sup>9</sup></code>
+*   `1 <= m <= n`

src/main/java/g3801_3900/s3808_find_emotionally_consistent_users/readme.md

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+3808\. Find Emotionally Consistent Users
+
+Medium
+
+Table: `reactions`
+
+    +--------------+---------+
+    | Column Name  | Type    |
+    +--------------+---------+
+    | user_id      | int     |
+    | content_id   | int     |
+    | reaction     | varchar |
+    +--------------+---------+
+
+(user_id, content_id) is the primary key (unique value) for this table.
+Each row represents a reaction given by a user to a piece of content.
+
+Write a solution to identify **emotionally consistent users** based on the following requirements:
+
+* For each user, count the total number of reactions they have given.
+* Only include users who have reacted to **at least** `5` **different content items**.
+* A user is considered **emotionally consistent** if **at least** `60%` of their reactions are of the **same type**.
+
+Return _the result table ordered by_ `reaction_ratio` _in **descending** order and then by_ `user_id` _in **ascending** order_.
+
+**Note:**
+
+* `reaction_ratio` should be rounded to `2` decimal places
+
+The result format is in the following example.
+
+**Example:**
+
+**Input:**
+
+reactions table:
+
+    +---------+------------+----------+
+    | user_id | content_id | reaction |
+    +---------+------------+----------+
+    | 1       | 101        | like     |
+    | 1       | 102        | like     |
+    | 1       | 103        | like     |
+    | 1       | 104        | wow      |
+    | 1       | 105        | like     |
+    | 2       | 201        | like     |
+    | 2       | 202        | wow      |
+    | 2       | 203        | sad      |
+    | 2       | 204        | like     |
+    | 2       | 205        | wow      |
+    | 3       | 301        | love     |
+    | 3       | 302        | love     |
+    | 3       | 303        | love     |
+    | 3       | 304        | love     |
+    | 3       | 305        | love     |
+    +---------+------------+----------+
+
+**Output:**
+
+    +---------+-------------------+----------------+
+    | user_id | dominant_reaction | reaction_ratio |
+    +---------+-------------------+----------------+
+    | 3       | love              | 1.00           |
+    | 1       | like              | 0.80           |
+    +---------+-------------------+----------------+
+
+**Explanation:**
+
+* **User 1**:
+    * Total reactions = 5
+    * like appears 4 times
+    * reaction_ratio = 4 / 5 = 0.80
+    * Meets the 60% consistency requirement
+* **User 2**:
+    * Total reactions = 5
+    * Most frequent reaction appears only 2 times
+    * reaction_ratio = 2 / 5 = 0.40
+    * Does not meet the consistency requirement
+* **User 3**:
+    * Total reactions = 5
+    * 'love' appears 5 times
+    * reaction_ratio = 5 / 5 = 1.00
+    * Meets the consistency requirement
+
+The Results table is ordered by reaction_ratio in descending order, then by user_id in ascending order.

src/main/java/g3801_3900/s3808_find_emotionally_consistent_users/script.sql

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+# #Medium #2026_06_09_Time_290_ms_(87.69%)_Space_0.0_MB_(100.00%)
+# Write your MySQL query statement below
+WITH user_selection AS
+(SELECT
+    user_id,
+    COUNT(reaction) AS total_reaction_count
+FROM
+    reactions
+GROUP BY
+    user_id
+HAVING
+    COUNT(DISTINCT content_id) >= 5
+),
+reaction_counts
+AS
+(SELECT
+    user_id,
+    reaction,
+    COUNT(*) AS reaction_count
+FROM
+reactions
+group by
+    user_id,
+    reaction
+),
+ranked_reactions AS (
+    -- Step 2: Use a window function to find the max for each user
+    SELECT
+        user_id,
+        reaction,
+        reaction_count,
+        RANK() OVER(PARTITION BY user_id ORDER BY reaction_count DESC) as rnk
+    FROM reaction_counts
+)
+SELECT
+    rc.user_id,
+    rc.reaction AS dominant_reaction,
+    ROUND(reaction_count / total_reaction_count, 2) AS reaction_ratio
+FROM
+    ranked_reactions rc
+INNER JOIN
+    user_selection us
+ON
+    rc.user_id = us.user_id
+WHERE
+    rc.rnk = 1
+    AND ROUND(reaction_count / total_reaction_count, 2) >= 0.60
+ORDER BY
+    3 DESC,
+    rc.user_id

src/main/java/g3801_3900/s3809_best_reachable_tower/Solution.java

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+package g3801_3900.s3809_best_reachable_tower;
+
+// #Medium #Array #Senior #Biweekly_Contest_174
+// #2026_06_09_Time_3_ms_(70.30%)_Space_219.56_MB_(26.73%)
+
+public class Solution {
+    public int[] bestTower(int[][] towers, int[] center, int radius) {
+        int bestX = -1;
+        int bestY = -1;
+        int bestQ = -1;
+        int cx = center[0];
+        int cy = center[1];
+        for (int[] t : towers) {
+            int x = t[0];
+            int y = t[1];
+            int q = t[2];
+            long dx = Math.abs((long) x - cx);
+            long dy = Math.abs((long) y - cy);
+            if (dx + dy <= radius
+                    && (q > bestQ
+                            || (q == bestQ
+                                    && (bestX == -1 || x < bestX || (x == bestX && y < bestY))))) {
+                bestQ = q;
+                bestX = x;
+                bestY = y;
+            }
+        }
+        return bestQ == -1 ? new int[] {-1, -1} : new int[] {bestX, bestY};
+    }
+}

src/main/java/g3801_3900/s3809_best_reachable_tower/readme.md

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+3809\. Best Reachable Tower
+
+Medium
+
+You are given a 2D integer array `towers`, where <code>towers[i] = [x<sub>i</sub>, y<sub>i</sub>, q<sub>i</sub>]</code> represents the coordinates <code>(x<sub>i</sub>, y<sub>i</sub>)</code> and quality factor <code>q<sub>i</sub></code> of the <code>i<sup>th</sup></code> tower.
+
+You are also given an integer array `center = [cx, cy]` representing your location, and an integer `radius`.
+
+A tower is **reachable** if its **Manhattan distance** from `center` is **less than or equal** to `radius`.
+
+Among all reachable towers:
+
+*   Return the coordinates of the tower with the **maximum** quality factor.
+*   If there is a tie, return the tower with the **lexicographically smallest** coordinate. If no tower is reachable, return `[-1, -1]`.
+
+The **Manhattan Distance** between two cells <code>(x<sub>i</sub>, y<sub>i</sub>)</code> and <code>(x<sub>j</sub>, y<sub>j</sub>)</code> is <code>|x<sub>i</sub> - x<sub>j</sub>| + |y<sub>i</sub> - y<sub>j</sub>|</code>.
+
+A coordinate <code>[x<sub>i</sub>, y<sub>i</sub>]</code> is **lexicographically smaller** than <code>[x<sub>j</sub>, y<sub>j</sub>]</code> if <code>x<sub>i</sub> < x<sub>j</sub></code>, or <code>x<sub>i</sub> == x<sub>j</sub></code> and <code>y<sub>i</sub> < y<sub>j</sub></code>.
+
+`|x|` denotes the **absolute** **value** of `x`.
+
+**Example 1:**
+
+**Input:** towers = [[1,2,5], [2,1,7], [3,1,9]], center = [1,1], radius = 2
+
+**Output:** [3,1]
+
+**Explanation:**
+
+*   Tower `[1, 2, 5]`: Manhattan distance = `|1 - 1| + |2 - 1| = 1`, reachable.
+*   Tower `[2, 1, 7]`: Manhattan distance = `|2 - 1| + |1 - 1| = 1`, reachable.
+*   Tower `[3, 1, 9]`: Manhattan distance = `|3 - 1| + |1 - 1| = 2`, reachable.
+
+All towers are reachable. The maximum quality factor is 9, which corresponds to tower `[3, 1]`.
+
+**Example 2:**
+
+**Input:** towers = [[1,3,4], [2,2,4], [4,4,7]], center = [0,0], radius = 5
+
+**Output:** [1,3]
+
+**Explanation:**
+
+*   Tower `[1, 3, 4]`: Manhattan distance = `|1 - 0| + |3 - 0| = 4`, reachable.
+*   Tower `[2, 2, 4]`: Manhattan distance = `|2 - 0| + |2 - 0| = 4`, reachable.
+*   Tower `[4, 4, 7]`: Manhattan distance = `|4 - 0| + |4 - 0| = 8`, not reachable.
+
+Among the reachable towers, the maximum quality factor is 4. Both `[1, 3]` and `[2, 2]` have the same quality, so the lexicographically smaller coordinate is `[1, 3]`.
+
+**Example 3:**
+
+**Input:** towers = [[5,6,8], [0,3,5]], center = [1,2], radius = 1
+
+**Output:** [-1,-1]
+
+**Explanation:**
+
+*   Tower `[5, 6, 8]`: Manhattan distance = `|5 - 1| + |6 - 2| = 8`, not reachable.
+*   Tower `[0, 3, 5]`: Manhattan distance = `|0 - 1| + |3 - 2| = 2`, not reachable.
+
+No tower is reachable within the given radius, so `[-1, -1]` is returned.
+
+**Constraints:**
+
+*   <code>1 <= towers.length <= 10<sup>5</sup></code>
+*   <code>towers[i] = [x<sub>i</sub>, y<sub>i</sub>, q<sub>i</sub>]</code>
+*   `center = [cx, cy]`
+*   <code>0 <= x<sub>i</sub>, y<sub>i</sub>, q<sub>i</sub>, cx, cy <= 10<sup>5</sup></code>
+*   <code>0 <= radius <= 10<sup>5</sup></code>

src/main/java/g3801_3900/s3810_minimum_operations_to_reach_target_array/Solution.java

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+package g3801_3900.s3810_minimum_operations_to_reach_target_array;
+
+// #Medium #Array #Hash_Table #Greedy #Senior #Biweekly_Contest_174
+// #2026_06_09_Time_24_ms_(89.58%)_Space_123.26_MB_(72.92%)
+
+import java.util.HashSet;
+import java.util.Set;
+
+public class Solution {
+    public int minOperations(int[] nums, int[] target) {
+        Set<Integer> virelantos = new HashSet<>();
+        for (int i = 0; i < nums.length; i++) {
+            if (nums[i] != target[i]) {
+                virelantos.add(nums[i]);
+            }
+        }
+        return virelantos.size();
+    }
+}