Added tasks 3038-3049

src/main/kotlin/g3001_3100/s3038_maximum_number_of_operations_with_the_same_score_i/Solution.kt

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+package g3001_3100.s3038_maximum_number_of_operations_with_the_same_score_i
+
+// #Easy #Array #Simulation #2024_03_06_Time_142_ms_(100.00%)_Space_34.9_MB_(57.78%)
+
+class Solution {
+    fun maxOperations(nums: IntArray): Int {
+        var c = 1
+        var i = 2
+        val s = nums[0] + nums[1]
+        val l = nums.size - (if (nums.size % 2 == 0) 0 else 1)
+        while (i < l) {
+            if (nums[i] + nums[i + 1] == s) {
+                c++
+            } else {
+                break
+            }
+            i += 2
+        }
+        return c
+    }
+}

src/main/kotlin/g3001_3100/s3038_maximum_number_of_operations_with_the_same_score_i/readme.md

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+3038\. Maximum Number of Operations With the Same Score I
+
+Easy
+
+Given an array of integers called `nums`, you can perform the following operation while `nums` contains **at least** `2` elements:
+
+*   Choose the first two elements of `nums` and delete them.
+
+The **score** of the operation is the sum of the deleted elements.
+
+Your task is to find the **maximum** number of operations that can be performed, such that **all operations have the same score**.
+
+Return _the **maximum** number of operations possible that satisfy the condition mentioned above_.
+
+**Example 1:**
+
+**Input:** nums = [3,2,1,4,5]
+
+**Output:** 2
+
+**Explanation:** We perform the following operations: 
+- Delete the first two elements, with score 3 + 2 = 5, nums = [1,4,5]. 
+- Delete the first two elements, with score 1 + 4 = 5, nums = [5]. 
+
+We are unable to perform any more operations as nums contain only 1 element.
+
+**Example 2:**
+
+**Input:** nums = [3,2,6,1,4]
+
+**Output:** 1
+
+**Explanation:** We perform the following operations: 
+- Delete the first two elements, with score 3 + 2 = 5, nums = [6,1,4]. 
+
+We are unable to perform any more operations as the score of the next operation isn't the same as the previous one.
+
+**Constraints:**
+
+*   `2 <= nums.length <= 100`
+*   `1 <= nums[i] <= 1000`

src/main/kotlin/g3001_3100/s3039_apply_operations_to_make_string_empty/Solution.kt

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+package g3001_3100.s3039_apply_operations_to_make_string_empty
+
+// #Medium #Array #Hash_Table #Sorting #Counting
+// #2024_03_06_Time_335_ms_(97.73%)_Space_49.8_MB_(81.82%)
+
+import kotlin.math.max
+
+class Solution {
+    fun lastNonEmptyString(s: String): String {
+        val freq = IntArray(26)
+        val ar = s.toCharArray()
+        val n = ar.size
+        var max = 1
+        val sb = StringBuilder()
+        for (c in ar) {
+            freq[c.code - 'a'.code]++
+            max = max(freq[c.code - 'a'.code].toDouble(), max.toDouble()).toInt()
+        }
+        for (i in n - 1 downTo 0) {
+            if (freq[ar[i].code - 'a'.code] == max) {
+                sb.append(ar[i])
+                freq[ar[i].code - 'a'.code] = 0
+            }
+        }
+        return sb.reverse().toString()
+    }
+}

src/main/kotlin/g3001_3100/s3039_apply_operations_to_make_string_empty/readme.md

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+3039\. Apply Operations to Make String Empty
+
+Medium
+
+You are given a string `s`.
+
+Consider performing the following operation until `s` becomes **empty**:
+
+*   For **every** alphabet character from `'a'` to `'z'`, remove the **first** occurrence of that character in `s` (if it exists).
+
+For example, let initially `s = "aabcbbca"`. We do the following operations:
+
+*   Remove the underlined characters <code>s = "<ins>**a**</ins>a**<ins>bc</ins>**bbca"</code>. The resulting string is `s = "abbca"`.
+*   Remove the underlined characters <code>s = "<ins>**ab**</ins>b<ins>**c**</ins>a"</code>. The resulting string is `s = "ba"`.
+*   Remove the underlined characters <code>s = "<ins>**ba**</ins>"</code>. The resulting string is `s = ""`.
+
+Return _the value of the string_ `s` _right **before** applying the **last** operation_. In the example above, answer is `"ba"`.
+
+**Example 1:**
+
+**Input:** s = "aabcbbca"
+
+**Output:** "ba"
+
+**Explanation:** Explained in the statement.
+
+**Example 2:**
+
+**Input:** s = "abcd"
+
+**Output:** "abcd"
+
+**Explanation:** We do the following operation: 
+- Remove the underlined characters s = "<ins>**abcd**</ins>". The resulting string is s = "". 
+
+The string just before the last operation is "abcd".
+
+**Constraints:**
+
+*   <code>1 <= s.length <= 5 * 10<sup>5</sup></code>
+*   `s` consists only of lowercase English letters.

src/main/kotlin/g3001_3100/s3040_maximum_number_of_operations_with_the_same_score_ii/Solution.kt

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+package g3001_3100.s3040_maximum_number_of_operations_with_the_same_score_ii
+
+// #Medium #Array #Dynamic_Programming #Memoization
+// #2024_03_06_Time_179_ms_(100.00%)_Space_38.4_MB_(100.00%)
+
+import java.util.Objects
+import kotlin.math.max
+
+class Solution {
+    private lateinit var nums: IntArray
+
+    private var maxOps = 1
+
+    private val dp: MutableMap<Pos, Int> = HashMap()
+
+    private class Pos(var start: Int, var end: Int, var sum: Int) {
+        override fun equals(other: Any?): Boolean {
+            if (other == null) {
+                return false
+            }
+            if (other !is Pos) {
+                return false
+            }
+            return start == other.start && end == other.end && sum == other.sum
+        }
+
+        override fun hashCode(): Int {
+            return Objects.hash(start, end, sum)
+        }
+    }
+
+    fun maxOperations(nums: IntArray): Int {
+        this.nums = nums
+        val length = nums.size
+
+        maxOperations(2, length - 1, nums[0] + nums[1], 1)
+        maxOperations(0, length - 3, nums[length - 2] + nums[length - 1], 1)
+        maxOperations(1, length - 2, nums[0] + nums[length - 1], 1)
+
+        return maxOps
+    }
+
+    private fun maxOperations(start: Int, end: Int, sum: Int, nOps: Int) {
+        if (start >= end) {
+            return
+        }
+
+        if ((((end - start) / 2) + nOps) < maxOps) {
+            return
+        }
+
+        val pos = Pos(start, end, sum)
+        val posNops = dp[pos]
+        if (posNops != null && posNops >= nOps) {
+            return
+        }
+        dp[pos] = nOps
+        if (nums[start] + nums[start + 1] == sum) {
+            maxOps = max(maxOps, (nOps + 1))
+            maxOperations(start + 2, end, sum, nOps + 1)
+        }
+        if (nums[end - 1] + nums[end] == sum) {
+            maxOps = max(maxOps, (nOps + 1))
+            maxOperations(start, end - 2, sum, nOps + 1)
+        }
+        if (nums[start] + nums[end] == sum) {
+            maxOps = max(maxOps, (nOps + 1))
+            maxOperations(start + 1, end - 1, sum, nOps + 1)
+        }
+    }
+}

src/main/kotlin/g3001_3100/s3040_maximum_number_of_operations_with_the_same_score_ii/readme.md

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+3040\. Maximum Number of Operations With the Same Score II
+
+Medium
+
+Given an array of integers called `nums`, you can perform **any** of the following operation while `nums` contains **at least** `2` elements:
+
+*   Choose the first two elements of `nums` and delete them.
+*   Choose the last two elements of `nums` and delete them.
+*   Choose the first and the last elements of `nums` and delete them.
+
+The **score** of the operation is the sum of the deleted elements.
+
+Your task is to find the **maximum** number of operations that can be performed, such that **all operations have the same score**.
+
+Return _the **maximum** number of operations possible that satisfy the condition mentioned above_.
+
+**Example 1:**
+
+**Input:** nums = [3,2,1,2,3,4]
+
+**Output:** 3
+
+**Explanation:** We perform the following operations: 
+- Delete the first two elements, with score 3 + 2 = 5, nums = [1,2,3,4]. 
+- Delete the first and the last elements, with score 1 + 4 = 5, nums = [2,3].
+- Delete the first and the last elements, with score 2 + 3 = 5, nums = []. 
+
+We are unable to perform any more operations as nums is empty.
+
+**Example 2:**
+
+**Input:** nums = [3,2,6,1,4]
+
+**Output:** 2
+
+**Explanation:** We perform the following operations: 
+- Delete the first two elements, with score 3 + 2 = 5, nums = [6,1,4]. 
+- Delete the last two elements, with score 1 + 4 = 5, nums = [6]. 
+
+It can be proven that we can perform at most 2 operations.
+
+**Constraints:**
+
+*   `2 <= nums.length <= 2000`
+*   `1 <= nums[i] <= 1000`

src/main/kotlin/g3001_3100/s3047_find_the_largest_area_of_square_inside_two_rectangles/Solution.kt

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+package g3001_3100.s3047_find_the_largest_area_of_square_inside_two_rectangles
+
+// #Medium #Array #Math #Geometry #2024_03_06_Time_753_ms_(40.42%)_Space_57.7_MB_(72.34%)
+
+import kotlin.math.max
+import kotlin.math.min
+import kotlin.math.pow
+
+class Solution {
+    fun largestSquareArea(bottomLeft: Array<IntArray>, topRight: Array<IntArray>): Long {
+        val n = bottomLeft.size
+        var maxArea: Long = 0
+        for (i in 0 until n) {
+            val ax = bottomLeft[i][0]
+            val ay = bottomLeft[i][1]
+            val bx = topRight[i][0]
+            val by = topRight[i][1]
+            for (j in i + 1 until n) {
+                val cx = bottomLeft[j][0]
+                val cy = bottomLeft[j][1]
+                val dx = topRight[j][0]
+                val dy = topRight[j][1]
+                val x1 = max(ax, cx)
+                val y1 = max(ay, cy)
+                val x2 = min(bx, dx)
+                val y2 = min(by, dy)
+                val minSide = min((x2 - x1), (y2 - y1))
+                val area = max(minSide.toDouble(), 0.0).pow(2.0).toLong()
+                maxArea = max(maxArea, area)
+            }
+        }
+        return maxArea
+    }
+}

src/main/kotlin/g3001_3100/s3047_find_the_largest_area_of_square_inside_two_rectangles/readme.md

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+3047\. Find the Largest Area of Square Inside Two Rectangles
+
+Medium
+
+There exist `n` rectangles in a 2D plane. You are given two **0-indexed** 2D integer arrays `bottomLeft` and `topRight`, both of size `n x 2`, where `bottomLeft[i]` and `topRight[i]` represent the **bottom-left** and **top-right** coordinates of the <code>i<sup>th</sup></code> rectangle respectively.
+
+You can select a region formed from the **intersection** of two of the given rectangles. You need to find the **largest** area of a **square** that can fit **inside** this region if you select the region optimally.
+
+Return _the **largest** possible area of a square, or_ `0` _if there **do not** exist any intersecting regions between the rectangles_.
+
+**Example 1:**
+
+![](https://assets.leetcode.com/uploads/2024/01/05/example12.png)
+
+**Input:** bottomLeft = [[1,1],[2,2],[3,1]], topRight = [[3,3],[4,4],[6,6]]
+
+**Output:** 1
+
+**Explanation:** A square with side length 1 can fit inside either the intersecting region of rectangle 0 and rectangle 1, or the intersecting region of rectangle 1 and rectangle 2. Hence the largest area is side \* side which is 1 \* 1 == 1.
+
+It can be shown that a square with a greater side length can not fit inside any intersecting region.
+
+**Example 2:**
+
+![](https://assets.leetcode.com/uploads/2024/01/04/rectanglesexample2.png)
+
+**Input:** bottomLeft = [[1,1],[2,2],[1,2]], topRight = [[3,3],[4,4],[3,4]]
+
+**Output:** 1
+
+**Explanation:** A square with side length 1 can fit inside either the intersecting region of rectangle 0 and rectangle 1, the intersecting region of rectangle 1 and rectangle 2, or the intersection region of all 3 rectangles. Hence the largest area is side \* side which is 1 \* 1 == 1.
+
+It can be shown that a square with a greater side length can not fit inside any intersecting region. Note that the region can be formed by the intersection of more than 2 rectangles.
+
+**Example 3:**
+
+![](https://assets.leetcode.com/uploads/2024/01/04/rectanglesexample3.png)
+
+**Input:** bottomLeft = [[1,1],[3,3],[3,1]], topRight = [[2,2],[4,4],[4,2]]
+
+**Output:** 0
+
+**Explanation:** No pair of rectangles intersect, hence, we return 0.
+
+**Constraints:**
+
+*   `n == bottomLeft.length == topRight.length`
+*   <code>2 <= n <= 10<sup>3</sup></code>
+*   `bottomLeft[i].length == topRight[i].length == 2`
+*   <code>1 <= bottomLeft[i][0], bottomLeft[i][1] <= 10<sup>7</sup></code>
+*   <code>1 <= topRight[i][0], topRight[i][1] <= 10<sup>7</sup></code>
+*   `bottomLeft[i][0] < topRight[i][0]`
+*   `bottomLeft[i][1] < topRight[i][1]`

src/main/kotlin/g3001_3100/s3048_earliest_second_to_mark_indices_i/Solution.kt

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+package g3001_3100.s3048_earliest_second_to_mark_indices_i
+
+// #Medium #Array #Binary_Search #2024_03_06_Time_223_ms_(75.00%)_Space_44.7_MB_(33.33%)
+
+class Solution {
+    fun earliestSecondToMarkIndices(nums: IntArray, changeIndices: IntArray): Int {
+        val n = nums.size
+        if (nums.isEmpty() || changeIndices.isEmpty()) {
+            return 0
+        }
+        val last = IntArray(n)
+        last.fill(-1)
+        for (i in changeIndices.indices) {
+            changeIndices[i] -= 1
+        }
+        var low = 0
+        var high = changeIndices.size - 1
+        while (low < high) {
+            val mid = low + (high - low) / 2
+            if (isPossible(mid, nums, changeIndices, last)) {
+                high = mid
+            } else {
+                low = mid + 1
+            }
+        }
+        return if (isPossible(low, nums, changeIndices, last)) low + 1 else -1
+    }
+
+    private fun isPossible(s: Int, nums: IntArray, changeIndices: IntArray, last: IntArray): Boolean {
+        val n = nums.size
+        last.fill(-1)
+        for (i in 0..s) {
+            last[changeIndices[i]] = i
+        }
+        var marked = 0
+        var operations = 0
+        for (i in 0..s) {
+            if (i == last[changeIndices[i]]) {
+                if (nums[changeIndices[i]] > operations) {
+                    return false
+                }
+                operations -= nums[changeIndices[i]]
+                marked++
+            } else {
+                operations++
+            }
+        }
+        return marked == n
+    }
+}