Added tasks 3643-3646

src/main/kotlin/g3601_3700/s3627_maximum_median_sum_of_subsequences_of_size_3/Solution.kt

@@ -1,6 +1,7 @@
 package g3601_3700.s3627_maximum_median_sum_of_subsequences_of_size_3
 
-// #Medium #Weekly_Contest_460 #2025_07_27_Time_46_ms_(91.67%)_Space_133.87_MB_(16.67%)
+// #Medium #Array #Math #Sorting #Greedy #Game_Theory #Weekly_Contest_460
+// #2025_07_27_Time_46_ms_(91.67%)_Space_133.87_MB_(16.67%)
 
 class Solution {
     fun maximumMedianSum(nums: IntArray): Long {

src/main/kotlin/g3601_3700/s3628_maximum_number_of_subsequences_after_one_inserting/Solution.kt

@@ -1,6 +1,7 @@
 package g3601_3700.s3628_maximum_number_of_subsequences_after_one_inserting
 
-// #Medium #Weekly_Contest_460 #2025_07_27_Time_13_ms_(100.00%)_Space_48.00_MB_(75.00%)
+// #Medium #String #Dynamic_Programming #Greedy #Prefix_Sum #Weekly_Contest_460
+// #2025_07_27_Time_13_ms_(100.00%)_Space_48.00_MB_(75.00%)
 
 class Solution {
     fun numOfSubsequences(s: String): Long {

src/main/kotlin/g3601_3700/s3629_minimum_jumps_to_reach_end_via_prime_teleportation/Solution.kt

@@ -1,6 +1,7 @@
 package g3601_3700.s3629_minimum_jumps_to_reach_end_via_prime_teleportation
 
-// #Medium #Weekly_Contest_460 #2025_07_27_Time_406_ms_(100.00%)_Space_153.64_MB_(100.00%)
+// #Medium #Array #Hash_Table #Math #Breadth_First_Search #Number_Theory #Weekly_Contest_460
+// #2025_07_27_Time_406_ms_(100.00%)_Space_153.64_MB_(100.00%)
 
 import java.util.ArrayDeque
 import kotlin.math.max

src/main/kotlin/g3601_3700/s3633_earliest_finish_time_for_land_and_water_rides_i/Solution.kt

@@ -1,6 +1,7 @@
 package g3601_3700.s3633_earliest_finish_time_for_land_and_water_rides_i
 
-// #Easy #Biweekly_Contest_162 #2025_08_03_Time_15_ms_(100.00%)_Space_48.53_MB_(100.00%)
+// #Easy #Array #Sorting #Greedy #Binary_Search #Two_Pointers #Biweekly_Contest_162
+// #2025_08_03_Time_15_ms_(100.00%)_Space_48.53_MB_(100.00%)
 
 import kotlin.math.max
 import kotlin.math.min

src/main/kotlin/g3601_3700/s3634_minimum_removals_to_balance_array/Solution.kt

@@ -1,6 +1,7 @@
 package g3601_3700.s3634_minimum_removals_to_balance_array
 
-// #Medium #Biweekly_Contest_162 #2025_08_03_Time_43_ms_(100.00%)_Space_66.87_MB_(100.00%)
+// #Medium #Array #Sorting #Sliding_Window #Biweekly_Contest_162
+// #2025_08_03_Time_43_ms_(100.00%)_Space_66.87_MB_(100.00%)
 
 import kotlin.math.max
 

src/main/kotlin/g3601_3700/s3635_earliest_finish_time_for_land_and_water_rides_ii/Solution.kt

@@ -1,6 +1,7 @@
 package g3601_3700.s3635_earliest_finish_time_for_land_and_water_rides_ii
 
-// #Medium #Biweekly_Contest_162 #2025_08_03_Time_5_ms_(100.00%)_Space_73.02_MB_(100.00%)
+// #Medium #Array #Sorting #Greedy #Binary_Search #Two_Pointers #Biweekly_Contest_162
+// #2025_08_03_Time_5_ms_(100.00%)_Space_73.02_MB_(100.00%)
 
 import kotlin.math.max
 import kotlin.math.min

src/main/kotlin/g3601_3700/s3636_threshold_majority_queries/Solution.kt

@@ -1,6 +1,7 @@
 package g3601_3700.s3636_threshold_majority_queries
 
-// #Hard #Biweekly_Contest_162 #2025_08_03_Time_848_ms_(100.00%)_Space_99.90_MB_(100.00%)
+// #Hard #Array #Hash_Table #Binary_Search #Prefix_Sum #Counting #Divide_and_Conquer
+// #Biweekly_Contest_162 #2025_08_03_Time_848_ms_(100.00%)_Space_99.90_MB_(100.00%)
 
 import java.util.TreeSet
 import kotlin.math.max

src/main/kotlin/g3601_3700/s3637_trionic_array_i/Solution.kt

@@ -1,29 +1,26 @@
 package g3601_3700.s3637_trionic_array_i
 
-// #Easy #Weekly_Contest_461 #2025_08_03_Time_1_ms_(100.00%)_Space_43.69_MB_(100.00%)
+// #Easy #Array #Weekly_Contest_461 #2025_08_14_Time_1_ms_(100.00%)_Space_43.95_MB_(38.57%)
 
 class Solution {
     fun isTrionic(nums: IntArray): Boolean {
-        var p = 0
-        var q = 0
+        var i = 1
         val n = nums.size
-        for (i in 1..<n - 1) {
-            if (nums[i - 1] == nums[i]) {
-                return false
-            }
-            if (nums[i - 1] < nums[i] && nums[i] > nums[i + 1]) {
-                if (p != 0) {
-                    return false
-                }
-                p = i
-            }
-            if (nums[i - 1] > nums[i] && nums[i] < nums[i + 1]) {
-                if (p == 0 || q != 0) {
-                    return false
-                }
-                q = i
-            }
+        while (i < n && nums[i] > nums[i - 1]) {
+            i++
         }
-        return q > 0
+        if (i == n || i == 1) {
+            return false
+        }
+        while (i < n && nums[i] < nums[i - 1]) {
+            i++
+        }
+        if (i == n) {
+            return false
+        }
+        while (i < n && nums[i] > nums[i - 1]) {
+            i++
+        }
+        return i == n
     }
 }

src/main/kotlin/g3601_3700/s3638_maximum_balanced_shipments/Solution.kt

@@ -1,6 +1,7 @@
 package g3601_3700.s3638_maximum_balanced_shipments
 
-// #Medium #Weekly_Contest_461 #2025_08_03_Time_5_ms_(100.00%)_Space_78.25_MB_(100.00%)
+// #Medium #Array #Dynamic_Programming #Greedy #Stack #Monotonic_Stack #Weekly_Contest_461
+// #2025_08_03_Time_5_ms_(100.00%)_Space_78.25_MB_(100.00%)
 
 import kotlin.math.max
 

src/main/kotlin/g3601_3700/s3639_minimum_time_to_activate_string/Solution.kt

@@ -1,34 +1,34 @@
 package g3601_3700.s3639_minimum_time_to_activate_string
 
-// #Medium #Weekly_Contest_461 #2025_08_03_Time_160_ms_(100.00%)_Space_85.36_MB_(100.00%)
-
-import java.util.TreeSet
+// #Medium #Array #Binary_Search #Weekly_Contest_461
+// #2025_08_14_Time_7_ms_(100.00%)_Space_79.04_MB_(50.00%)
 
 class Solution {
     fun minTime(s: String, order: IntArray, k: Int): Int {
         val n = s.length
-        // Use a TreeSet to maintain a sorted list of indices
-        val pos = TreeSet<Int?>()
-        pos.add(-1)
-        pos.add(n)
-        // Iterate through the order of removal
-        var localK = k
-        for (t in order.indices) {
+        var total = n * (n + 1L) / 2
+        if (total < k) {
+            return -1
+        }
+        val prev = IntArray(n + 1)
+        val next = IntArray(n + 1)
+        for (i in 0..<n) {
+            prev[i] = i - 1
+            next[i] = i + 1
+        }
+        for (t in n - 1 downTo 0) {
             val i = order[t]
-            // Find the elements in the sorted set that bracket the current index 'i'
-            // 'r' is the smallest element >= i
-            val r = pos.ceiling(i)
-            // 'l' is the largest element <= i
-            val l = pos.floor(i)
-            // The 'cost' to remove an item is the product of the distances to its neighbors
-            localK -= ((i - l!!).toLong() * (r!! - i)).toInt()
-            pos.add(i)
-            // If the total cost is exhausted, return the current time 't'
-            if (localK <= 0) {
+            val left = prev[i]
+            val right = next[i]
+            total -= (i - left).toLong() * (right - i)
+            if (total < k) {
                 return t
             }
+            if (left >= 0) {
+                next[left] = right
+            }
+            prev[right] = left
         }
-        // If all items are removed and k is not exhausted, return -1
-        return -1
+        return 0
     }
 }

src/main/kotlin/g3601_3700/s3640_trionic_array_ii/Solution.kt

@@ -1,6 +1,7 @@
 package g3601_3700.s3640_trionic_array_ii
 
-// #Hard #Weekly_Contest_461 #2025_08_03_Time_7_ms_(100.00%)_Space_79.14_MB_(100.00%)
+// #Hard #Array #Dynamic_Programming #Weekly_Contest_461
+// #2025_08_03_Time_7_ms_(100.00%)_Space_79.14_MB_(100.00%)
 
 import kotlin.math.max
 

src/main/kotlin/g3601_3700/s3643_flip_square_submatrix_vertically/Solution.kt

@@ -0,0 +1,19 @@
+package g3601_3700.s3643_flip_square_submatrix_vertically
+
+// #Easy #Array #Matrix #Two_Pointers #Weekly_Contest_462
+// #2025_08_11_Time_1_ms_(100.00%)_Space_49.92_MB_(100.00%)
+
+class Solution {
+    fun reverseSubmatrix(grid: Array<IntArray>, x: Int, y: Int, k: Int): Array<IntArray> {
+        for (i in 0..<k / 2) {
+            val top = x + i
+            val bottom = x + k - 1 - i
+            for (col in 0..<k) {
+                val temp = grid[top][y + col]
+                grid[top][y + col] = grid[bottom][y + col]
+                grid[bottom][y + col] = temp
+            }
+        }
+        return grid
+    }
+}

src/main/kotlin/g3601_3700/s3643_flip_square_submatrix_vertically/readme.md

@@ -0,0 +1,45 @@
+3643\. Flip Square Submatrix Vertically
+
+Easy
+
+You are given an `m x n` integer matrix `grid`, and three integers `x`, `y`, and `k`.
+
+The integers `x` and `y` represent the row and column indices of the **top-left** corner of a **square** submatrix and the integer `k` represents the size (side length) of the square submatrix.
+
+Your task is to flip the submatrix by reversing the order of its rows vertically.
+
+Return the updated matrix.
+
+**Example 1:**
+
+![](https://assets.leetcode.com/uploads/2025/07/20/gridexmdrawio.png)
+
+**Input:** grid = [[1,2,3,4],[5,6,7,8],[9,10,11,12],[13,14,15,16]], x = 1, y = 0, k = 3
+
+**Output:** [[1,2,3,4],[13,14,15,8],[9,10,11,12],[5,6,7,16]]
+
+**Explanation:**
+
+The diagram above shows the grid before and after the transformation.
+
+**Example 2:**
+
+![](https://assets.leetcode.com/uploads/2025/07/20/gridexm2drawio.png)
+
+**Input:** grid = [[3,4,2,3],[2,3,4,2]], x = 0, y = 2, k = 2
+
+**Output:** [[3,4,4,2],[2,3,2,3]]
+
+**Explanation:**
+
+The diagram above shows the grid before and after the transformation.
+
+**Constraints:**
+
+*   `m == grid.length`
+*   `n == grid[i].length`
+*   `1 <= m, n <= 50`
+*   `1 <= grid[i][j] <= 100`
+*   `0 <= x < m`
+*   `0 <= y < n`
+*   `1 <= k <= min(m - x, n - y)`

src/main/kotlin/g3601_3700/s3644_maximum_k_to_sort_a_permutation/Solution.kt

@@ -0,0 +1,24 @@
+package g3601_3700.s3644_maximum_k_to_sort_a_permutation
+
+// #Medium #Weekly_Contest_462 #2025_08_11_Time_4_ms_(100.00%)_Space_83.96_MB_(100.00%)
+
+class Solution {
+    fun sortPermutation(nums: IntArray): Int {
+        val n = nums.size
+        var res = -1
+        for (i in 0..<n) {
+            if (nums[i] == i) {
+                continue
+            }
+            if (res == -1) {
+                res = nums[i]
+            } else {
+                res = res and nums[i]
+            }
+        }
+        if (res == -1) {
+            return 0
+        }
+        return res
+    }
+}

src/main/kotlin/g3601_3700/s3644_maximum_k_to_sort_a_permutation/readme.md

@@ -0,0 +1,47 @@
+3644\. Maximum K to Sort a Permutation
+
+Medium
+
+You are given an integer array `nums` of length `n`, where `nums` is a **permutation** of the numbers in the range `[0..n - 1]`.
+
+You may swap elements at indices `i` and `j` **only if** `nums[i] AND nums[j] == k`, where `AND` denotes the bitwise AND operation and `k` is a **non-negative** integer.
+
+Return the **maximum** value of `k` such that the array can be sorted in **non-decreasing** order using any number of such swaps. If `nums` is already sorted, return 0.
+
+A **permutation** is a rearrangement of all the elements of an array.
+
+**Example 1:**
+
+**Input:** nums = [0,3,2,1]
+
+**Output:** 1
+
+**Explanation:**
+
+Choose `k = 1`. Swapping `nums[1] = 3` and `nums[3] = 1` is allowed since `nums[1] AND nums[3] == 1`, resulting in a sorted permutation: `[0, 1, 2, 3]`.
+
+**Example 2:**
+
+**Input:** nums = [0,1,3,2]
+
+**Output:** 2
+
+**Explanation:**
+
+Choose `k = 2`. Swapping `nums[2] = 3` and `nums[3] = 2` is allowed since `nums[2] AND nums[3] == 2`, resulting in a sorted permutation: `[0, 1, 2, 3]`.
+
+**Example 3:**
+
+**Input:** nums = [3,2,1,0]
+
+**Output:** 0
+
+**Explanation:**
+
+Only `k = 0` allows sorting since no greater `k` allows the required swaps where `nums[i] AND nums[j] == k`.
+
+**Constraints:**
+
+*   <code>1 <= n == nums.length <= 10<sup>5</sup></code>
+*   `0 <= nums[i] <= n - 1`
+*   `nums` is a permutation of integers from `0` to `n - 1`.

src/main/kotlin/g3601_3700/s3645_maximum_total_from_optimal_activation_order/Solution.kt

@@ -0,0 +1,34 @@
+package g3601_3700.s3645_maximum_total_from_optimal_activation_order
+
+// #Medium #Array #Sorting #Greedy #Two_Pointers #Heap_Priority_Queue #Weekly_Contest_462
+// #2025_08_11_Time_77_ms_(100.00%)_Space_88.24_MB_(100.00%)
+
+import java.util.Collections
+import kotlin.math.min
+
+class Solution {
+    fun maxTotal(value: IntArray, limit: IntArray): Long {
+        val n = value.size
+        val groups: Array<MutableList<Int>?> = arrayOfNulls<MutableList<Int>>(n + 1)
+        for (i in 0..<n) {
+            val l = limit[i]
+            if (groups[l] == null) {
+                groups[l] = ArrayList<Int>()
+            }
+            groups[l]!!.add(value[i])
+        }
+        var total: Long = 0
+        for (l in 1..n) {
+            val list = groups[l]
+            if (list == null) {
+                continue
+            }
+            list.sortWith(Collections.reverseOrder<Int>())
+            val cap = min(l, list.size)
+            for (i in 0..<cap) {
+                total += list[i].toLong()
+            }
+        }
+        return total
+    }
+}