Added tasks 3200-3203

src/main/kotlin/g3101_3200/s3200_maximum_height_of_a_triangle/Solution.kt

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+package g3101_3200.s3200_maximum_height_of_a_triangle
+
+// #Easy #Array #Enumeration #2024_07_06_Time_136_ms_(81.36%)_Space_33.8_MB_(28.81%)
+
+import kotlin.math.max
+
+@Suppress("NAME_SHADOWING")
+class Solution {
+    private fun count(v1: Int, v2: Int): Int {
+        var v1 = v1
+        var v2 = v2
+        var ct = 1
+        var flag = true
+        while (true) {
+            if (flag) {
+                if (ct <= v1) {
+                    v1 -= ct
+                } else {
+                    break
+                }
+            } else {
+                if (ct <= v2) {
+                    v2 -= ct
+                } else {
+                    break
+                }
+            }
+            ct++
+            flag = !flag
+        }
+        return ct - 1
+    }
+
+    fun maxHeightOfTriangle(red: Int, blue: Int): Int {
+        return max(count(red, blue), count(blue, red))
+    }
+}

src/main/kotlin/g3101_3200/s3200_maximum_height_of_a_triangle/readme.md

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+3200\. Maximum Height of a Triangle
+
+Easy
+
+You are given two integers `red` and `blue` representing the count of red and blue colored balls. You have to arrange these balls to form a triangle such that the 1<sup>st</sup> row will have 1 ball, the 2<sup>nd</sup> row will have 2 balls, the 3<sup>rd</sup> row will have 3 balls, and so on.
+
+All the balls in a particular row should be the **same** color, and adjacent rows should have **different** colors.
+
+Return the **maximum** _height of the triangle_ that can be achieved.
+
+**Example 1:**
+
+**Input:** red = 2, blue = 4
+
+**Output:** 3
+
+**Explanation:**
+
+![](https://assets.leetcode.com/uploads/2024/06/16/brb.png)
+
+The only possible arrangement is shown above.
+
+**Example 2:**
+
+**Input:** red = 2, blue = 1
+
+**Output:** 2
+
+**Explanation:**
+
+![](https://assets.leetcode.com/uploads/2024/06/16/br.png)   
+ The only possible arrangement is shown above.
+
+**Example 3:**
+
+**Input:** red = 1, blue = 1
+
+**Output:** 1
+
+**Example 4:**
+
+**Input:** red = 10, blue = 1
+
+**Output:** 2
+
+**Explanation:**
+
+![](https://assets.leetcode.com/uploads/2024/06/16/br.png)   
+ The only possible arrangement is shown above.
+
+**Constraints:**
+
+*   `1 <= red, blue <= 100`

src/main/kotlin/g3201_3300/s3201_find_the_maximum_length_of_valid_subsequence_i/Solution.kt

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+package g3201_3300.s3201_find_the_maximum_length_of_valid_subsequence_i
+
+// #Medium #Array #Dynamic_Programming #2024_07_06_Time_512_ms_(89.36%)_Space_62.1_MB_(76.60%)
+
+import kotlin.math.max
+
+class Solution {
+    fun maximumLength(nums: IntArray): Int {
+        val n = nums.size
+        var alter = 1
+        var odd = 0
+        var even = 0
+        if (nums[0] % 2 == 0) {
+            even++
+        } else {
+            odd++
+        }
+        var lastodd = nums[0] % 2 != 0
+        for (i in 1 until n) {
+            val flag = nums[i] % 2 == 0
+            if (flag) {
+                if (lastodd) {
+                    alter++
+                    lastodd = false
+                }
+                even++
+            } else {
+                if (!lastodd) {
+                    alter++
+                    lastodd = true
+                }
+                odd++
+            }
+        }
+        return max(alter, max(odd, even))
+    }
+}

src/main/kotlin/g3201_3300/s3201_find_the_maximum_length_of_valid_subsequence_i/readme.md

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+3201\. Find the Maximum Length of Valid Subsequence I
+
+Medium
+
+You are given an integer array `nums`.
+
+A subsequence `sub` of `nums` with length `x` is called **valid** if it satisfies:
+
+*   `(sub[0] + sub[1]) % 2 == (sub[1] + sub[2]) % 2 == ... == (sub[x - 2] + sub[x - 1]) % 2.`
+
+Return the length of the **longest** **valid** subsequence of `nums`.
+
+A **subsequence** is an array that can be derived from another array by deleting some or no elements without changing the order of the remaining elements.
+
+**Example 1:**
+
+**Input:** nums = [1,2,3,4]
+
+**Output:** 4
+
+**Explanation:**
+
+The longest valid subsequence is `[1, 2, 3, 4]`.
+
+**Example 2:**
+
+**Input:** nums = [1,2,1,1,2,1,2]
+
+**Output:** 6
+
+**Explanation:**
+
+The longest valid subsequence is `[1, 2, 1, 2, 1, 2]`.
+
+**Example 3:**
+
+**Input:** nums = [1,3]
+
+**Output:** 2
+
+**Explanation:**
+
+The longest valid subsequence is `[1, 3]`.
+
+**Constraints:**
+
+*   <code>2 <= nums.length <= 2 * 10<sup>5</sup></code>
+*   <code>1 <= nums[i] <= 10<sup>7</sup></code>

src/main/kotlin/g3201_3300/s3202_find_the_maximum_length_of_valid_subsequence_ii/Solution.kt

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+package g3201_3300.s3202_find_the_maximum_length_of_valid_subsequence_ii
+
+// #Medium #Array #Dynamic_Programming #2024_07_06_Time_255_ms_(97.30%)_Space_49_MB_(78.38%)
+
+import kotlin.math.max
+
+class Solution {
+    fun maximumLength(nums: IntArray, k: Int): Int {
+        // dp array to store the index against each possible modulo
+        val dp = Array(nums.size + 1) { IntArray(k + 1) }
+        var longest = 0
+        for (i in nums.indices) {
+            for (j in 0 until i) {
+                // Checking the modulo with each previous number
+                val `val` = (nums[i] + nums[j]) % k
+                // storing the number of pairs that have the same modulo.
+                // it would be one more than the number of pairs with the same modulo at the last
+                // index
+                dp[i][`val`] = dp[j][`val`] + 1
+                // Calculating the max seen till now
+                longest = max(longest, dp[i][`val`])
+            }
+        }
+        // total number of elements in the subsequence would be 1 more than the number of pairs
+        return longest + 1
+    }
+}

src/main/kotlin/g3201_3300/s3202_find_the_maximum_length_of_valid_subsequence_ii/readme.md

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+3202\. Find the Maximum Length of Valid Subsequence II
+
+Medium
+
+You are given an integer array `nums` and a **positive** integer `k`.
+
+A subsequence `sub` of `nums` with length `x` is called **valid** if it satisfies:
+
+*   `(sub[0] + sub[1]) % k == (sub[1] + sub[2]) % k == ... == (sub[x - 2] + sub[x - 1]) % k.`
+
+Return the length of the **longest** **valid** subsequence of `nums`.
+
+**Example 1:**
+
+**Input:** nums = [1,2,3,4,5], k = 2
+
+**Output:** 5
+
+**Explanation:**
+
+The longest valid subsequence is `[1, 2, 3, 4, 5]`.
+
+**Example 2:**
+
+**Input:** nums = [1,4,2,3,1,4], k = 3
+
+**Output:** 4
+
+**Explanation:**
+
+The longest valid subsequence is `[1, 4, 1, 4]`.
+
+**Constraints:**
+
+*   <code>2 <= nums.length <= 10<sup>3</sup></code>
+*   <code>1 <= nums[i] <= 10<sup>7</sup></code>
+*   <code>1 <= k <= 10<sup>3</sup></code>

src/main/kotlin/g3201_3300/s3203_find_minimum_diameter_after_merging_two_trees/Solution.kt

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+package g3201_3300.s3203_find_minimum_diameter_after_merging_two_trees
+
+// #Hard #Depth_First_Search #Breadth_First_Search #Tree #Graph
+// #2024_07_06_Time_1156_ms_(100.00%)_Space_119.4_MB_(80.00%)
+
+import kotlin.math.max
+
+class Solution {
+    fun minimumDiameterAfterMerge(edges1: Array<IntArray>, edges2: Array<IntArray>): Int {
+        val n = edges1.size + 1
+        val g = packU(n, edges1)
+        val m = edges2.size + 1
+        val h = packU(m, edges2)
+        val d1 = diameter(g)
+        val d2 = diameter(h)
+        var ans = max(d1[0], d2[0])
+        ans = max(
+            ((d1[0] + 1) / 2 + ((d2[0] + 1) / 2) + 1),
+            ans
+        )
+        return ans
+    }
+
+    private fun diameter(g: Array<IntArray?>): IntArray {
+        val n = g.size
+        val f0: Int
+        val f1: Int
+        val d01: Int
+        val q = IntArray(n)
+        val ved = BooleanArray(n)
+        var qp = 0
+        q[qp++] = 0
+        ved[0] = true
+        run {
+            var i = 0
+            while (i < qp) {
+                val cur = q[i]
+                for (e in g[cur]!!) {
+                    if (!ved[e]) {
+                        ved[e] = true
+                        q[qp++] = e
+                    }
+                }
+                i++
+            }
+        }
+        f0 = q[n - 1]
+        val d = IntArray(n)
+        qp = 0
+        ved.fill(false)
+        q[qp++] = f0
+        ved[f0] = true
+        var i = 0
+        while (i < qp) {
+            val cur = q[i]
+            for (e in g[cur]!!) {
+                if (!ved[e]) {
+                    ved[e] = true
+                    q[qp++] = e
+                    d[e] = d[cur] + 1
+                }
+            }
+            i++
+        }
+        f1 = q[n - 1]
+        d01 = d[f1]
+        return intArrayOf(d01, f0, f1)
+    }
+
+    private fun packU(n: Int, ft: Array<IntArray>): Array<IntArray?> {
+        val g = arrayOfNulls<IntArray>(n)
+        val p = IntArray(n)
+        for (u in ft) {
+            p[u[0]]++
+            p[u[1]]++
+        }
+        for (i in 0 until n) {
+            g[i] = IntArray(p[i])
+        }
+        for (u in ft) {
+            g[u[0]]!![--p[u[0]]] = u[1]
+            g[u[1]]!![--p[u[1]]] = u[0]
+        }
+        return g
+    }
+}

src/main/kotlin/g3201_3300/s3203_find_minimum_diameter_after_merging_two_trees/readme.md

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+3203\. Find Minimum Diameter After Merging Two Trees
+
+Hard
+
+There exist two **undirected** trees with `n` and `m` nodes, numbered from `0` to `n - 1` and from `0` to `m - 1`, respectively. You are given two 2D integer arrays `edges1` and `edges2` of lengths `n - 1` and `m - 1`, respectively, where <code>edges1[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 first tree and <code>edges2[i] = [u<sub>i</sub>, v<sub>i</sub>]</code> indicates that there is an edge between nodes <code>u<sub>i</sub></code> and <code>v<sub>i</sub></code> in the second tree.
+
+You must connect one node from the first tree with another node from the second tree with an edge.
+
+Return the **minimum** possible **diameter** of the resulting tree.
+
+The **diameter** of a tree is the length of the _longest_ path between any two nodes in the tree.
+
+**Example 1:**![](https://assets.leetcode.com/uploads/2024/04/22/example11-transformed.png)
+
+**Input:** edges1 = [[0,1],[0,2],[0,3]], edges2 = [[0,1]]
+
+**Output:** 3
+
+**Explanation:**
+
+We can obtain a tree of diameter 3 by connecting node 0 from the first tree with any node from the second tree.
+
+**Example 2:**
+
+![](https://assets.leetcode.com/uploads/2024/04/22/example211.png)
+
+**Input:** edges1 = [[0,1],[0,2],[0,3],[2,4],[2,5],[3,6],[2,7]], edges2 = [[0,1],[0,2],[0,3],[2,4],[2,5],[3,6],[2,7]]
+
+**Output:** 5
+
+**Explanation:**
+
+We can obtain a tree of diameter 5 by connecting node 0 from the first tree with node 0 from the second tree.
+
+**Constraints:**
+
+*   <code>1 <= n, m <= 10<sup>5</sup></code>
+*   `edges1.length == n - 1`
+*   `edges2.length == m - 1`
+*   `edges1[i].length == edges2[i].length == 2`
+*   <code>edges1[i] = [a<sub>i</sub>, b<sub>i</sub>]</code>
+*   <code>0 <= a<sub>i</sub>, b<sub>i</sub> < n</code>
+*   <code>edges2[i] = [u<sub>i</sub>, v<sub>i</sub>]</code>
+*   <code>0 <= u<sub>i</sub>, v<sub>i</sub> < m</code>
+*   The input is generated such that `edges1` and `edges2` represent valid trees.

src/test/kotlin/g3101_3200/s3200_maximum_height_of_a_triangle/SolutionTest.kt

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+package g3101_3200.s3200_maximum_height_of_a_triangle
+
+import org.hamcrest.CoreMatchers.equalTo
+import org.hamcrest.MatcherAssert.assertThat
+import org.junit.jupiter.api.Test
+
+internal class SolutionTest {
+    @Test
+    fun maxHeightOfTriangle() {
+        assertThat(Solution().maxHeightOfTriangle(2, 4), equalTo(3))
+    }
+
+    @Test
+    fun maxHeightOfTriangle2() {
+        assertThat(Solution().maxHeightOfTriangle(2, 1), equalTo(2))
+    }
+}