Added tasks 3673-3677

src/main/java/g3601_3700/s3673_find_zombie_sessions/readme.md

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+3673\. Find Zombie Sessions
+
+Hard
+
+Table: `app_events`
+
+    +------------------+----------+
+    | Column Name      | Type     |
+    +------------------+----------+
+    | event_id         | int      |
+    | user_id          | int      |
+    | event_timestamp  | datetime |
+    | event_type       | varchar  |
+    | session_id       | varchar  |
+    | event_value      | int      |
+    +------------------+----------+
+    event_id is the unique identifier for this table.
+    event_type can be app_open, click, scroll, purchase, or app_close.
+    session_id groups events within the same user session.
+    event_value represents: for purchase - amount in dollars, for scroll - pixels scrolled, for others - NULL. 
+
+Write a solution to identify **zombie sessions, **sessions where users appear active but show abnormal behavior patterns. A session is considered a **zombie session** if it meets ALL the following criteria:
+
+*   The session duration is **more than** `30` minutes.
+*   Has **at least** `5` scroll events.
+*   The **click-to-scroll ratio** is less than `0.20` .
+*   **No purchases** were made during the session.
+
+Return _the result table ordered by_ `scroll_count` _in **descending** order, then by_ `session_id` _in **ascending** order_.
+
+The result format is in the following example.
+
+**Example:**
+
+**Input:**
+
+app\_events table:
+
+    +----------+---------+---------------------+------------+------------+-------------+
+    | event_id | user_id | event_timestamp     | event_type | session_id | event_value |
+    +----------+---------+---------------------+------------+------------+-------------+
+    | 1        | 201     | 2024-03-01 10:00:00 | app_open   | S001       | NULL        |
+    | 2        | 201     | 2024-03-01 10:05:00 | scroll     | S001       | 500         |
+    | 3        | 201     | 2024-03-01 10:10:00 | scroll     | S001       | 750         |
+    | 4        | 201     | 2024-03-01 10:15:00 | scroll     | S001       | 600         |
+    | 5        | 201     | 2024-03-01 10:20:00 | scroll     | S001       | 800         |
+    | 6        | 201     | 2024-03-01 10:25:00 | scroll     | S001       | 550         |
+    | 7        | 201     | 2024-03-01 10:30:00 | scroll     | S001       | 900         |
+    | 8        | 201     | 2024-03-01 10:35:00 | app_close  | S001       | NULL        |
+    | 9        | 202     | 2024-03-01 11:00:00 | app_open   | S002       | NULL        |
+    | 10       | 202     | 2024-03-01 11:02:00 | click      | S002       | NULL        |
+    | 11       | 202     | 2024-03-01 11:05:00 | scroll     | S002       | 400         |
+    | 12       | 202     | 2024-03-01 11:08:00 | click      | S002       | NULL        |
+    | 13       | 202     | 2024-03-01 11:10:00 | scroll     | S002       | 350         |
+    | 14       | 202     | 2024-03-01 11:15:00 | purchase   | S002       | 50          |
+    | 15       | 202     | 2024-03-01 11:20:00 | app_close  | S002       | NULL        |
+    | 16       | 203     | 2024-03-01 12:00:00 | app_open   | S003       | NULL        |
+    | 17       | 203     | 2024-03-01 12:10:00 | scroll     | S003       | 1000        |
+    | 18       | 203     | 2024-03-01 12:20:00 | scroll     | S003       | 1200        |
+    | 19       | 203     | 2024-03-01 12:25:00 | click      | S003       | NULL        |
+    | 20       | 203     | 2024-03-01 12:30:00 | scroll     | S003       | 800         |
+    | 21       | 203     | 2024-03-01 12:40:00 | scroll     | S003       | 900         |
+    | 22       | 203     | 2024-03-01 12:50:00 | scroll     | S003       | 1100        |
+    | 23       | 203     | 2024-03-01 13:00:00 | app_close  | S003       | NULL        |
+    | 24       | 204     | 2024-03-01 14:00:00 | app_open   | S004       | NULL        |
+    | 25       | 204     | 2024-03-01 14:05:00 | scroll     | S004       | 600         |
+    | 26       | 204     | 2024-03-01 14:08:00 | scroll     | S004       | 700         |
+    | 27       | 204     | 2024-03-01 14:10:00 | click      | S004       | NULL        |
+    | 28       | 204     | 2024-03-01 14:12:00 | app_close  | S004       | NULL        |
+    +----------+---------+---------------------+------------+------------+-------------+
+
+**Output:**
+
+    +------------+---------+--------------------------+--------------+
+    | session_id | user_id | session_duration_minutes | scroll_count |
+    +------------+---------+--------------------------+--------------+
+    | S001       | 201     | 35                       | 6            |
+    +------------+---------+--------------------------+--------------+
+
+**Explanation:**
+
+*   **Session S001 (User 201)**:
+    *   Duration: 10:00:00 to 10:35:00 = 35 minutes (more than 30)
+    *   Scroll events: 6 (at least 5)
+    *   Click events: 0
+    *   Click-to-scroll ratio: 0/6 = 0.00 (less than 0.20)
+    *   Purchases: 0 (no purchases)
+    *   S001 is a zombie session (meets all criteria)
+*   **Session S002 (User 202)**:
+    *   Duration: 11:00:00 to 11:20:00 = 20 minutes (less than 30)
+    *   Has a purchase event
+    *   S002 is not a zombie session
+*   **Session S003 (User 203)**:
+    *   Duration: 12:00:00 to 13:00:00 = 60 minutes (more than 30)
+    *   Scroll events: 5 (at least 5)
+    *   Click events: 1
+    *   Click-to-scroll ratio: 1/5 = 0.20 (not less than 0.20)
+    *   Purchases: 0 (no purchases)
+    *   S003 is not a zombie session (click-to-scroll ratio equals 0.20, needs to be less)
+*   **Session S004 (User 204)**:
+    *   Duration: 14:00:00 to 14:12:00 = 12 minutes (less than 30)
+    *   Scroll events: 2 (less than 5)
+    *   S004 is not a zombie session
+
+The result table is ordered by scroll\_count in descending order, then by session\_id in ascending order.

src/main/java/g3601_3700/s3673_find_zombie_sessions/script.sql

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+# Write your MySQL query statement below
+# #Hard #Database #2025_09_07_Time_278_ms_(100.00%)_Space_0.0_MB_(100.00%)
+SELECT
+    session_id,
+    user_id,
+    TIMESTAMPDIFF(MINUTE, MIN(event_timestamp), MAX(event_timestamp)) AS session_duration_minutes,
+    SUM(CASE WHEN event_type = 'scroll' THEN 1 ELSE 0 END) AS scroll_count -- NOSONAR
+FROM
+    app_events
+GROUP BY
+    session_id,
+    user_id
+HAVING
+    TIMESTAMPDIFF(MINUTE, MIN(event_timestamp), MAX(event_timestamp)) > 30
+    AND SUM(CASE WHEN event_type = 'scroll' THEN 1 ELSE 0 END) > 4 -- NOSONAR
+    AND (
+        CAST(SUM(CASE WHEN event_type = 'click' THEN 1 ELSE 0 END) AS DOUBLE) /
+        NULLIF(SUM(CASE WHEN event_type = 'scroll' THEN 1 ELSE 0 END), 0) -- NOSONAR
+    ) < 0.2
+    AND SUM(CASE WHEN event_type = 'purchase' THEN 1 ELSE 0 END) = 0
+ORDER BY
+    scroll_count DESC,
+    session_id ASC;

src/main/java/g3601_3700/s3674_minimum_operations_to_equalize_array/Solution.java

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+package g3601_3700.s3674_minimum_operations_to_equalize_array;
+
+// #Easy #Weekly_Contest_466 #2025_09_07_Time_1_ms_(100.00%)_Space_43.98_MB_(100.00%)
+
+public class Solution {
+    public int minOperations(int[] nums) {
+        for (int num : nums) {
+            if (num != nums[0]) {
+                return 1;
+            }
+        }
+        return 0;
+    }
+}

src/main/java/g3601_3700/s3674_minimum_operations_to_equalize_array/readme.md

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+3674\. Minimum Operations to Equalize Array
+
+Easy
+
+You are given an integer array `nums` of length `n`.
+
+In one operation, choose any subarray `nums[l...r]` (`0 <= l <= r < n`) and **replace** each element in that subarray with the **bitwise AND** of all elements.
+
+Return the **minimum** number of operations required to make all elements of `nums` equal.
+
+A **subarray** is a contiguous **non-empty** sequence of elements within an array.
+
+**Example 1:**
+
+**Input:** nums = [1,2]
+
+**Output:** 1
+
+**Explanation:**
+
+Choose `nums[0...1]`: `(1 AND 2) = 0`, so the array becomes `[0, 0]` and all elements are equal in 1 operation.
+
+**Example 2:**
+
+**Input:** nums = [5,5,5]
+
+**Output:** 0
+
+**Explanation:**
+
+`nums` is `[5, 5, 5]` which already has all elements equal, so 0 operations are required.
+
+**Constraints:**
+
+*   `1 <= n == nums.length <= 100`
+*   <code>1 <= nums[i] <= 10<sup>5</sup></code>

src/main/java/g3601_3700/s3675_minimum_operations_to_transform_string/Solution.java

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+package g3601_3700.s3675_minimum_operations_to_transform_string;
+
+// #Medium #Weekly_Contest_466 #2025_09_14_Time_5_ms_(100.00%)_Space_47.93_MB_(95.06%)
+
+public class Solution {
+    public int minOperations(String s) {
+        int n = s.length();
+        int ans = 0;
+        for (int i = 0; i < n; i++) {
+            final char c = s.charAt(i);
+            if (c != 'a') {
+                int ops = 'z' - c + 1;
+                if (ops > ans) {
+                    ans = ops;
+                }
+                if (ops == 25) {
+                    break;
+                }
+            }
+        }
+        return ans;
+    }
+}

src/main/java/g3601_3700/s3675_minimum_operations_to_transform_string/readme.md

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+3675\. Minimum Operations to Transform String
+
+Medium
+
+You are given a string `s` consisting only of lowercase English letters.
+
+You can perform the following operation any number of times (including zero):
+
+*   Choose any character `c` in the string and replace **every** occurrence of `c` with the **next** lowercase letter in the English alphabet.
+
+
+Return the **minimum** number of operations required to transform `s` into a string consisting of **only** `'a'` characters.
+
+**Note:** Consider the alphabet as circular, thus `'a'` comes after `'z'`.
+
+**Example 1:**
+
+**Input:** s = "yz"
+
+**Output:** 2
+
+**Explanation:**
+
+*   Change `'y'` to `'z'` to get `"zz"`.
+*   Change `'z'` to `'a'` to get `"aa"`.
+*   Thus, the answer is 2.
+
+**Example 2:**
+
+**Input:** s = "a"
+
+**Output:** 0
+
+**Explanation:**
+
+*   The string `"a"` only consists of `'a'` characters. Thus, the answer is 0.
+
+**Constraints:**
+
+*   <code>1 <= s.length <= 5 * 10<sup>5</sup></code>
+*   `s` consists only of lowercase English letters.

src/main/java/g3601_3700/s3676_count_bowl_subarrays/Solution.java

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+package g3601_3700.s3676_count_bowl_subarrays;
+
+// #Medium #Weekly_Contest_466 #2025_09_14_Time_2_ms_(100.00%)_Space_58.91_MB_(69.85%)
+
+public class Solution {
+    public long bowlSubarrays(int[] nums) {
+        int n = nums.length;
+        int res = n;
+        int pre = 0;
+        for (int a : nums) {
+            if (a > pre) {
+                res--;
+                pre = a;
+            }
+        }
+        pre = 0;
+        for (int i = n - 1; i >= 0; i--) {
+            if (nums[i] > pre) {
+                res--;
+                pre = nums[i];
+            }
+        }
+        return res + 1L;
+    }
+}

src/main/java/g3601_3700/s3676_count_bowl_subarrays/readme.md

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+3676\. Count Bowl Subarrays
+
+Medium
+
+You are given an integer array `nums` with **distinct** elements.
+
+A subarray `nums[l...r]` of `nums` is called a **bowl** if:
+
+*   The subarray has length at least 3. That is, `r - l + 1 >= 3`.
+*   The **minimum** of its two ends is **strictly greater** than the **maximum** of all elements in between. That is, `min(nums[l], nums[r]) > max(nums[l + 1], ..., nums[r - 1])`.
+
+Return the number of **bowl** subarrays in `nums`.
+
+**Example 1:**
+
+**Input:** nums = [2,5,3,1,4]
+
+**Output:** 2
+
+**Explanation:**
+
+The bowl subarrays are `[3, 1, 4]` and `[5, 3, 1, 4]`.
+
+*   `[3, 1, 4]` is a bowl because `min(3, 4) = 3 > max(1) = 1`.
+*   `[5, 3, 1, 4]` is a bowl because `min(5, 4) = 4 > max(3, 1) = 3`.
+
+**Example 2:**
+
+**Input:** nums = [5,1,2,3,4]
+
+**Output:** 3
+
+**Explanation:**
+
+The bowl subarrays are `[5, 1, 2]`, `[5, 1, 2, 3]` and `[5, 1, 2, 3, 4]`.
+
+**Example 3:**
+
+**Input:** nums = [1000000000,999999999,999999998]
+
+**Output:** 0
+
+**Explanation:**
+
+No subarray is a bowl.
+
+**Constraints:**
+
+*   <code>3 <= nums.length <= 10<sup>5</sup></code>
+*   <code>1 <= nums[i] <= 10<sup>9</sup></code>
+*   `nums` consists of distinct elements.

src/main/java/g3601_3700/s3677_count_binary_palindromic_numbers/Solution.java

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+package g3601_3700.s3677_count_binary_palindromic_numbers;
+
+// #Hard #Weekly_Contest_466 #2025_09_07_Time_1_ms_(100.00%)_Space_40.86_MB_(100.00%)
+
+public class Solution {
+    private long makePalin(long left, boolean odd) {
+        long ans = left;
+        if (odd) {
+            left = left >> 1;
+        }
+        while (left > 0) {
+            ans = (ans << 1) | (left & 1);
+            left = left >> 1;
+        }
+        return ans;
+    }
+
+    public int countBinaryPalindromes(long n) {
+        if (n == 0) {
+            return 1;
+        }
+        int len = 64 - Long.numberOfLeadingZeros(n);
+        long count = 1;
+        for (int i = 1; i < len; i++) {
+            int half = (i + 1) / 2;
+            count += 1L << (half - 1);
+        }
+        int half = (len + 1) / 2;
+        long prefix = n >> (len - half);
+        long palin = makePalin(prefix, len % 2 == 1);
+        count += (prefix - (1L << (half - 1)));
+        if (palin <= n) {
+            ++count;
+        }
+        return (int) count;
+    }
+}