diff --git a/src/main/kotlin/g2501_2600/s2600_k_items_with_the_maximum_sum/Solution.kt b/src/main/kotlin/g2501_2600/s2600_k_items_with_the_maximum_sum/Solution.kt
new file mode 100644
index 000000000..c062dcb27
--- /dev/null
+++ b/src/main/kotlin/g2501_2600/s2600_k_items_with_the_maximum_sum/Solution.kt
@@ -0,0 +1,20 @@
+package g2501_2600.s2600_k_items_with_the_maximum_sum
+
+// #Easy #Math #Greedy #2023_07_13_Time_145_ms_(100.00%)_Space_33.5_MB_(75.00%)
+
+@Suppress("UNUSED_PARAMETER")
+class Solution {
+    fun kItemsWithMaximumSum(numOnes: Int, numZeros: Int, numNegOnes: Int, k: Int): Int {
+        if (k <= numOnes) {
+            return k
+        }
+
+        if (k <= numOnes + numZeros) {
+            return numOnes
+        }
+
+        val remainingSum = k - (numOnes + numZeros)
+
+        return numOnes - remainingSum
+    }
+}
diff --git a/src/main/kotlin/g2501_2600/s2600_k_items_with_the_maximum_sum/readme.md b/src/main/kotlin/g2501_2600/s2600_k_items_with_the_maximum_sum/readme.md
new file mode 100644
index 000000000..c791a9fd9
--- /dev/null
+++ b/src/main/kotlin/g2501_2600/s2600_k_items_with_the_maximum_sum/readme.md
@@ -0,0 +1,36 @@
+2600\. K Items With the Maximum Sum
+
+Easy
+
+There is a bag that consists of items, each item has a number `1`, `0`, or `-1` written on it.
+
+You are given four **non-negative** integers `numOnes`, `numZeros`, `numNegOnes`, and `k`.
+
+The bag initially contains:
+
+*   `numOnes` items with `1`s written on them.
+*   `numZeroes` items with `0`s written on them.
+*   `numNegOnes` items with `-1`s written on them.
+
+We want to pick exactly `k` items among the available items. Return _the **maximum** possible sum of numbers written on the items_.
+
+**Example 1:**
+
+**Input:** numOnes = 3, numZeros = 2, numNegOnes = 0, k = 2
+
+**Output:** 2
+
+**Explanation:** We have a bag of items with numbers written on them {1, 1, 1, 0, 0}. We take 2 items with 1 written on them and get a sum in a total of 2. It can be proven that 2 is the maximum possible sum.
+
+**Example 2:**
+
+**Input:** numOnes = 3, numZeros = 2, numNegOnes = 0, k = 4
+
+**Output:** 3
+
+**Explanation:** We have a bag of items with numbers written on them {1, 1, 1, 0, 0}. We take 3 items with 1 written on them, and 1 item with 0 written on it, and get a sum in a total of 3. It can be proven that 3 is the maximum possible sum.
+
+**Constraints:**
+
+*   `0 <= numOnes, numZeros, numNegOnes <= 50`
+*   `0 <= k <= numOnes + numZeros + numNegOnes`
\ No newline at end of file
diff --git a/src/main/kotlin/g2601_2700/s2601_prime_subtraction_operation/Solution.kt b/src/main/kotlin/g2601_2700/s2601_prime_subtraction_operation/Solution.kt
new file mode 100644
index 000000000..122e47205
--- /dev/null
+++ b/src/main/kotlin/g2601_2700/s2601_prime_subtraction_operation/Solution.kt
@@ -0,0 +1,44 @@
+package g2601_2700.s2601_prime_subtraction_operation
+
+// #Medium #Array #Math #Greedy #Binary_Search #Number_Theory
+// #2023_07_13_Time_233_ms_(100.00%)_Space_38.4_MB_(100.00%)
+
+class Solution {
+    private fun primesUntil(n: Int): IntArray {
+        if (n < 2) return intArrayOf()
+        val primes = IntArray(200)
+        val composite = BooleanArray(n + 1)
+        primes[0] = 2
+        var added = 1
+        var i = 3
+        while (i <= n) {
+            if (composite[i]) {
+                i += 2
+                continue
+            }
+            primes[added++] = i
+            var j = i * i
+            while (j <= n) {
+                composite[j] = true
+                j += i
+            }
+            i += 2
+        }
+        return primes.copyOf(added)
+    }
+
+    fun primeSubOperation(nums: IntArray): Boolean {
+        var max = 0
+        for (n in nums) {
+            max = max.coerceAtLeast(n)
+        }
+        val primes = primesUntil(max)
+        var prev = 0
+        for (n in nums) {
+            val pos = primes.binarySearch(n - prev - 1)
+            if (pos == -1 && n <= prev) return false
+            prev = n - if (pos == -1) 0 else if (pos < 0) primes[-pos - 2] else primes[pos]
+        }
+        return true
+    }
+}
diff --git a/src/main/kotlin/g2601_2700/s2601_prime_subtraction_operation/readme.md b/src/main/kotlin/g2601_2700/s2601_prime_subtraction_operation/readme.md
new file mode 100644
index 000000000..23dc5ce40
--- /dev/null
+++ b/src/main/kotlin/g2601_2700/s2601_prime_subtraction_operation/readme.md
@@ -0,0 +1,43 @@
+2601\. Prime Subtraction Operation
+
+Medium
+
+You are given a **0-indexed** integer array `nums` of length `n`.
+
+You can perform the following operation as many times as you want:
+
+*   Pick an index `i` that you haven’t picked before, and pick a prime `p` **strictly less than** `nums[i]`, then subtract `p` from `nums[i]`.
+
+Return _true if you can make `nums` a strictly increasing array using the above operation and false otherwise._
+
+A **strictly increasing array** is an array whose each element is strictly greater than its preceding element.
+
+**Example 1:**
+
+**Input:** nums = [4,9,6,10]
+
+**Output:** true
+
+**Explanation:** In the first operation: Pick i = 0 and p = 3, and then subtract 3 from nums[0], so that nums becomes [1,9,6,10]. In the second operation: i = 1, p = 7, subtract 7 from nums[1], so nums becomes equal to [1,2,6,10]. After the second operation, nums is sorted in strictly increasing order, so the answer is true.
+
+**Example 2:**
+
+**Input:** nums = [6,8,11,12]
+
+**Output:** true
+
+**Explanation:** Initially nums is sorted in strictly increasing order, so we don't need to make any operations.
+
+**Example 3:**
+
+**Input:** nums = [5,8,3]
+
+**Output:** false
+
+**Explanation:** It can be proven that there is no way to perform operations to make nums sorted in strictly increasing order, so the answer is false.
+
+**Constraints:**
+
+*   `1 <= nums.length <= 1000`
+*   `1 <= nums[i] <= 1000`
+*   `nums.length == n`
\ No newline at end of file
diff --git a/src/main/kotlin/g2601_2700/s2602_minimum_operations_to_make_all_array_elements_equal/Solution.kt b/src/main/kotlin/g2601_2700/s2602_minimum_operations_to_make_all_array_elements_equal/Solution.kt
new file mode 100644
index 000000000..68881d44b
--- /dev/null
+++ b/src/main/kotlin/g2601_2700/s2602_minimum_operations_to_make_all_array_elements_equal/Solution.kt
@@ -0,0 +1,41 @@
+package g2601_2700.s2602_minimum_operations_to_make_all_array_elements_equal
+
+// #Medium #Array #Sorting #Binary_Search #Prefix_Sum
+// #2023_07_13_Time_790_ms_(100.00%)_Space_63.8_MB_(100.00%)
+
+class Solution {
+    fun minOperations(nums: IntArray, queries: IntArray): List<Long> {
+        nums.sort()
+        val sum = LongArray(nums.size)
+        sum[0] = nums[0].toLong()
+        for (i in 1 until nums.size) {
+            sum[i] = sum[i - 1] + nums[i].toLong()
+        }
+        val res: MutableList<Long> = ArrayList()
+        for (query in queries) {
+            res.add(getOperations(sum, nums, query))
+        }
+        return res
+    }
+
+    private fun getOperations(sum: LongArray, nums: IntArray, target: Int): Long {
+        var res: Long = 0
+        val index = getIndex(nums, target)
+        val rightCounts = nums.size - 1 - index
+        if (index > 0) {
+            res += index.toLong() * target - sum[index - 1]
+        }
+        if (rightCounts > 0) {
+            res += sum[nums.size - 1] - sum[index] - rightCounts.toLong() * target
+        }
+        res += kotlin.math.abs(target - nums[index]).toLong()
+        return res
+    }
+
+    private fun getIndex(nums: IntArray, target: Int): Int {
+        var index = nums.binarySearch(target)
+        if (index < 0) index = -(index + 1)
+        if (index == nums.size) --index
+        return index
+    }
+}
diff --git a/src/main/kotlin/g2601_2700/s2602_minimum_operations_to_make_all_array_elements_equal/readme.md b/src/main/kotlin/g2601_2700/s2602_minimum_operations_to_make_all_array_elements_equal/readme.md
new file mode 100644
index 000000000..515f388ec
--- /dev/null
+++ b/src/main/kotlin/g2601_2700/s2602_minimum_operations_to_make_all_array_elements_equal/readme.md
@@ -0,0 +1,49 @@
+2602\. Minimum Operations to Make All Array Elements Equal
+
+Medium
+
+You are given an array `nums` consisting of positive integers.
+
+You are also given an integer array `queries` of size `m`. For the <code>i<sup>th</sup></code> query, you want to make all of the elements of `nums` equal to `queries[i]`. You can perform the following operation on the array **any** number of times:
+
+*   **Increase** or **decrease** an element of the array by `1`.
+
+Return _an array_ `answer` _of size_ `m` _where_ `answer[i]` _is the **minimum** number of operations to make all elements of_ `nums` _equal to_ `queries[i]`.
+
+**Note** that after each query the array is reset to its original state.
+
+**Example 1:**
+
+**Input:** nums = [3,1,6,8], queries = [1,5]
+
+**Output:** [14,10]
+
+**Explanation:** For the first query we can do the following operations: 
+- Decrease nums[0] 2 times, so that nums = [1,1,6,8]. 
+- Decrease nums[2] 5 times, so that nums = [1,1,1,8]. 
+- Decrease nums[3] 7 times, so that nums = [1,1,1,1]. 
+
+So the total number of operations for the first query is 2 + 5 + 7 = 14. 
+
+For the second query we can do the following operations: 
+- Increase nums[0] 2 times, so that nums = [5,1,6,8]. 
+- Increase nums[1] 4 times, so that nums = [5,5,6,8]. 
+- Decrease nums[2] 1 time, so that nums = [5,5,5,8]. 
+- Decrease nums[3] 3 times, so that nums = [5,5,5,5]. 
+
+So the total number of operations for the second query is 2 + 4 + 1 + 3 = 10.
+
+**Example 2:**
+
+**Input:** nums = [2,9,6,3], queries = [10]
+
+**Output:** [20]
+
+**Explanation:** We can increase each value in the array to 10. The total number of operations will be 8 + 1 + 4 + 7 = 20.
+
+**Constraints:**
+
+*   `n == nums.length`
+*   `m == queries.length`
+*   <code>1 <= n, m <= 10<sup>5</sup></code>
+*   <code>1 <= nums[i], queries[i] <= 10<sup>9</sup></code>
\ No newline at end of file
diff --git a/src/main/kotlin/g2601_2700/s2603_collect_coins_in_a_tree/Solution.kt b/src/main/kotlin/g2601_2700/s2603_collect_coins_in_a_tree/Solution.kt
new file mode 100644
index 000000000..1652d2314
--- /dev/null
+++ b/src/main/kotlin/g2601_2700/s2603_collect_coins_in_a_tree/Solution.kt
@@ -0,0 +1,50 @@
+package g2601_2700.s2603_collect_coins_in_a_tree
+
+// #Hard #Array #Tree #Graph #Topological_Sort
+// #2023_07_13_Time_986_ms_(100.00%)_Space_67.7_MB_(100.00%)
+
+class Solution {
+    private lateinit var coins: IntArray
+    private var n = 0
+    private lateinit var graph: Array<ArrayList<Int>?>
+    private var sum = 0
+    private var ret = 0
+    fun collectTheCoins(coins: IntArray, edges: Array<IntArray>): Int {
+        n = coins.size
+        this.coins = coins
+        graph = arrayOfNulls(n)
+        for (i in 0 until n) {
+            graph[i] = ArrayList()
+        }
+        for (edge in edges) {
+            graph[edge[0]]!!.add(edge[1])
+            graph[edge[1]]!!.add(edge[0])
+        }
+        for (coin in coins) {
+            sum += coin
+        }
+        dfs(0, -1)
+        return (2 * (ret - 1)).coerceAtLeast(0)
+    }
+
+    private fun dfs(node: Int, pre: Int): Int {
+        var cnt = 0
+        var s = 0
+        for (nn in graph[node]!!) {
+            if (nn != pre) {
+                val r = dfs(nn, node)
+                if (r - coins[nn] > 0) cnt++
+                s += r
+            }
+        }
+
+        if (pre != -1 && sum - s - coins[node] - coins[pre] > 0) {
+            cnt++
+        }
+
+        if (cnt >= 2) {
+            ret++
+        }
+        return s + coins[node]
+    }
+}
diff --git a/src/main/kotlin/g2601_2700/s2603_collect_coins_in_a_tree/readme.md b/src/main/kotlin/g2601_2700/s2603_collect_coins_in_a_tree/readme.md
new file mode 100644
index 000000000..e43338609
--- /dev/null
+++ b/src/main/kotlin/g2601_2700/s2603_collect_coins_in_a_tree/readme.md
@@ -0,0 +1,45 @@
+2603\. Collect Coins in a Tree
+
+Hard
+
+There exists an undirected and unrooted tree with `n` nodes indexed from `0` to `n - 1`. You are given an integer `n` and a 2D integer array edges of length `n - 1`, where <code>edges[i] = [a<sub>i</sub>, b<sub>i</sub>]</code> indicates that there is an edge between nodes <code>a<sub>i</sub></code> and <code>b<sub>i</sub></code> in the tree. You are also given an array `coins` of size `n` where `coins[i]` can be either `0` or `1`, where `1` indicates the presence of a coin in the vertex `i`.
+
+Initially, you choose to start at any vertex in the tree. Then, you can perform the following operations any number of times:
+
+*   Collect all the coins that are at a distance of at most `2` from the current vertex, or
+*   Move to any adjacent vertex in the tree.
+
+Find _the minimum number of edges you need to go through to collect all the coins and go back to the initial vertex_.
+
+Note that if you pass an edge several times, you need to count it into the answer several times.
+
+**Example 1:**
+
+![](https://assets.leetcode.com/uploads/2023/03/01/graph-2.png)
+
+**Input:** coins = [1,0,0,0,0,1], edges = [[0,1],[1,2],[2,3],[3,4],[4,5]]
+
+**Output:** 2
+
+**Explanation:** Start at vertex 2, collect the coin at vertex 0, move to vertex 3, collect the coin at vertex 5 then move back to vertex 2.
+
+**Example 2:**
+
+![](https://assets.leetcode.com/uploads/2023/03/02/graph-4.png)
+
+**Input:** coins = [0,0,0,1,1,0,0,1], edges = [[0,1],[0,2],[1,3],[1,4],[2,5],[5,6],[5,7]]
+
+**Output:** 2
+
+**Explanation:** Start at vertex 0, collect the coins at vertices 4 and 3, move to vertex 2, collect the coin at vertex 7, then move back to vertex 0.
+
+**Constraints:**
+
+*   `n == coins.length`
+*   <code>1 <= n <= 3 * 10<sup>4</sup></code>
+*   `0 <= coins[i] <= 1`
+*   `edges.length == n - 1`
+*   `edges[i].length == 2`
+*   <code>0 <= a<sub>i</sub>, b<sub>i</sub> < n</code>
+*   <code>a<sub>i</sub> != b<sub>i</sub></code>
+*   `edges` represents a valid tree.
\ No newline at end of file
diff --git a/src/main/kotlin/g2601_2700/s2605_form_smallest_number_from_two_digit_arrays/Solution.kt b/src/main/kotlin/g2601_2700/s2605_form_smallest_number_from_two_digit_arrays/Solution.kt
new file mode 100644
index 000000000..5f0e240f8
--- /dev/null
+++ b/src/main/kotlin/g2601_2700/s2605_form_smallest_number_from_two_digit_arrays/Solution.kt
@@ -0,0 +1,20 @@
+package g2601_2700.s2605_form_smallest_number_from_two_digit_arrays
+
+// #Easy #Array #Hash_Table #Enumeration #2023_07_13_Time_161_ms_(100.00%)_Space_34.7_MB_(100.00%)
+
+class Solution {
+    fun minNumber(nums1: IntArray, nums2: IntArray): Int {
+        val set = HashSet<Int>()
+        var (min, min1, min2) = arrayOf(10, 10, 10)
+        for (num in nums1) {
+            min1 = minOf(min1, num)
+            set.add(num)
+        }
+        for (num in nums2) {
+            min2 = minOf(min2, num)
+            if (set.contains(num)) min = minOf(min, num)
+        }
+        if (min != 10) return min
+        return minOf(min1, min2) * 10 + maxOf(min1, min2)
+    }
+}
diff --git a/src/main/kotlin/g2601_2700/s2605_form_smallest_number_from_two_digit_arrays/readme.md b/src/main/kotlin/g2601_2700/s2605_form_smallest_number_from_two_digit_arrays/readme.md
new file mode 100644
index 000000000..7243c63b9
--- /dev/null
+++ b/src/main/kotlin/g2601_2700/s2605_form_smallest_number_from_two_digit_arrays/readme.md
@@ -0,0 +1,27 @@
+2605\. Form Smallest Number From Two Digit Arrays
+
+Easy
+
+Given two arrays of **unique** digits `nums1` and `nums2`, return _the **smallest** number that contains **at least** one digit from each array_.
+
+**Example 1:**
+
+**Input:** nums1 = [4,1,3], nums2 = [5,7]
+
+**Output:** 15
+
+**Explanation:** The number 15 contains the digit 1 from nums1 and the digit 5 from nums2. It can be proven that 15 is the smallest number we can have.
+
+**Example 2:**
+
+**Input:** nums1 = [3,5,2,6], nums2 = [3,1,7]
+
+**Output:** 3
+
+**Explanation:** The number 3 contains the digit 3 which exists in both arrays.
+
+**Constraints:**
+
+*   `1 <= nums1.length, nums2.length <= 9`
+*   `1 <= nums1[i], nums2[i] <= 9`
+*   All digits in each array are **unique**.
\ No newline at end of file
diff --git a/src/test/kotlin/g2501_2600/s2600_k_items_with_the_maximum_sum/SolutionTest.kt b/src/test/kotlin/g2501_2600/s2600_k_items_with_the_maximum_sum/SolutionTest.kt
new file mode 100644
index 000000000..8b67dd3d1
--- /dev/null
+++ b/src/test/kotlin/g2501_2600/s2600_k_items_with_the_maximum_sum/SolutionTest.kt
@@ -0,0 +1,17 @@
+package g2501_2600.s2600_k_items_with_the_maximum_sum
+
+import org.hamcrest.CoreMatchers.equalTo
+import org.hamcrest.MatcherAssert.assertThat
+import org.junit.jupiter.api.Test
+
+internal class SolutionTest {
+    @Test
+    fun kItemsWithMaximumSum() {
+        assertThat(Solution().kItemsWithMaximumSum(3, 2, 0, 2), equalTo(2))
+    }
+
+    @Test
+    fun kItemsWithMaximumSum2() {
+        assertThat(Solution().kItemsWithMaximumSum(3, 2, 0, 4), equalTo(3))
+    }
+}
diff --git a/src/test/kotlin/g2601_2700/s2601_prime_subtraction_operation/SolutionTest.kt b/src/test/kotlin/g2601_2700/s2601_prime_subtraction_operation/SolutionTest.kt
new file mode 100644
index 000000000..05a477f0b
--- /dev/null
+++ b/src/test/kotlin/g2601_2700/s2601_prime_subtraction_operation/SolutionTest.kt
@@ -0,0 +1,22 @@
+package g2601_2700.s2601_prime_subtraction_operation
+
+import org.hamcrest.CoreMatchers.equalTo
+import org.hamcrest.MatcherAssert.assertThat
+import org.junit.jupiter.api.Test
+
+internal class SolutionTest {
+    @Test
+    fun primeSubOperation() {
+        assertThat(Solution().primeSubOperation(intArrayOf(4, 9, 6, 10)), equalTo(true))
+    }
+
+    @Test
+    fun primeSubOperation2() {
+        assertThat(Solution().primeSubOperation(intArrayOf(6, 8, 11, 12)), equalTo(true))
+    }
+
+    @Test
+    fun primeSubOperation3() {
+        assertThat(Solution().primeSubOperation(intArrayOf(5, 8, 3)), equalTo(false))
+    }
+}
diff --git a/src/test/kotlin/g2601_2700/s2602_minimum_operations_to_make_all_array_elements_equal/SolutionTest.kt b/src/test/kotlin/g2601_2700/s2602_minimum_operations_to_make_all_array_elements_equal/SolutionTest.kt
new file mode 100644
index 000000000..b426a9ed8
--- /dev/null
+++ b/src/test/kotlin/g2601_2700/s2602_minimum_operations_to_make_all_array_elements_equal/SolutionTest.kt
@@ -0,0 +1,17 @@
+package g2601_2700.s2602_minimum_operations_to_make_all_array_elements_equal
+
+import org.hamcrest.CoreMatchers.equalTo
+import org.hamcrest.MatcherAssert.assertThat
+import org.junit.jupiter.api.Test
+
+internal class SolutionTest {
+    @Test
+    fun minOperations() {
+        assertThat(Solution().minOperations(intArrayOf(3, 1, 6, 8), intArrayOf(1, 5)), equalTo(listOf(14L, 10L)))
+    }
+
+    @Test
+    fun minOperations2() {
+        assertThat(Solution().minOperations(intArrayOf(2, 9, 6, 3), intArrayOf(10)), equalTo(listOf(20L)))
+    }
+}
diff --git a/src/test/kotlin/g2601_2700/s2603_collect_coins_in_a_tree/SolutionTest.kt b/src/test/kotlin/g2601_2700/s2603_collect_coins_in_a_tree/SolutionTest.kt
new file mode 100644
index 000000000..03708378b
--- /dev/null
+++ b/src/test/kotlin/g2601_2700/s2603_collect_coins_in_a_tree/SolutionTest.kt
@@ -0,0 +1,37 @@
+package g2601_2700.s2603_collect_coins_in_a_tree
+
+import org.hamcrest.CoreMatchers.equalTo
+import org.hamcrest.MatcherAssert.assertThat
+import org.junit.jupiter.api.Test
+
+internal class SolutionTest {
+    @Test
+    fun collectTheCoins() {
+        assertThat(
+            Solution().collectTheCoins(
+                intArrayOf(1, 0, 0, 0, 0, 1),
+                arrayOf(
+                    intArrayOf(0, 1),
+                    intArrayOf(1, 2), intArrayOf(2, 3),
+                    intArrayOf(3, 4), intArrayOf(4, 5)
+                )
+            ),
+            equalTo(2)
+        )
+    }
+
+    @Test
+    fun collectTheCoins2() {
+        assertThat(
+            Solution().collectTheCoins(
+                intArrayOf(0, 0, 0, 1, 1, 0, 0, 1),
+                arrayOf(
+                    intArrayOf(0, 1),
+                    intArrayOf(0, 2), intArrayOf(1, 3), intArrayOf(1, 4), intArrayOf(2, 5),
+                    intArrayOf(5, 6), intArrayOf(5, 7)
+                )
+            ),
+            equalTo(2)
+        )
+    }
+}
diff --git a/src/test/kotlin/g2601_2700/s2605_form_smallest_number_from_two_digit_arrays/SolutionTest.kt b/src/test/kotlin/g2601_2700/s2605_form_smallest_number_from_two_digit_arrays/SolutionTest.kt
new file mode 100644
index 000000000..bbdc0e12e
--- /dev/null
+++ b/src/test/kotlin/g2601_2700/s2605_form_smallest_number_from_two_digit_arrays/SolutionTest.kt
@@ -0,0 +1,17 @@
+package g2601_2700.s2605_form_smallest_number_from_two_digit_arrays
+
+import org.hamcrest.CoreMatchers.equalTo
+import org.hamcrest.MatcherAssert.assertThat
+import org.junit.jupiter.api.Test
+
+internal class SolutionTest {
+    @Test
+    fun minNumber() {
+        assertThat(Solution().minNumber(intArrayOf(4, 1, 3), intArrayOf(5, 7)), equalTo(15))
+    }
+
+    @Test
+    fun minNumber2() {
+        assertThat(Solution().minNumber(intArrayOf(3, 5, 2, 6), intArrayOf(3, 1, 7)), equalTo(3))
+    }
+}