0298-binary-tree-longest-consecutive-sequence

Author: bofeizhu

0298-binary-tree-longest-consecutive-sequence.playground/Contents.swift

@@ -0,0 +1,53 @@
+/// 298. Binary Tree Longest Consecutive Sequence
+/// Given a binary tree, find the length of the longest consecutive sequence path. The path refers
+/// to any sequence of nodes from some starting node to any node in the tree along the parent-child
+/// connections. The longest consecutive path need to be from parent to child (cannot be the
+/// reverse).
+
+import XCTest
+
+final class TreeNode {
+    var val: Int
+    var left: TreeNode?
+    var right: TreeNode?
+    init(_ val: Int) {
+        self.val = val
+        self.left = nil
+        self.right = nil
+    }
+}
+
+/// Approach: DFS
+func longestConsecutive(_ root: TreeNode?) -> Int {
+    var maxLength = 0
+    func dfs(_ node: TreeNode?) -> Int {
+        if let node = node {
+            var leftLength = dfs(node.left) + 1
+            var rightLength = dfs(node.right) + 1
+            if let left = node.left,
+               node.val + 1 != left.val {
+                leftLength = 1
+            }
+            
+            if let right = node.right,
+               node.val + 1 != right.val {
+                rightLength = 1
+            }
+            let length = max(leftLength, rightLength)
+            maxLength = max(length, maxLength)
+            return length
+        } else {
+            return 0
+        }
+    }
+    dfs(root)
+    return maxLength
+}
+
+class Tests: XCTestCase {
+    func testExample() {
+        // TODO: Add test case
+    }
+}
+
+Tests.defaultTestSuite.run()

0298-binary-tree-longest-consecutive-sequence.playground/contents.xcplayground

@@ -0,0 +1,4 @@
+<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
+<playground version='5.0' target-platform='macos' executeOnSourceChanges='false'>
+    <timeline fileName='timeline.xctimeline'/>
+</playground>

README.md

@@ -58,6 +58,7 @@ You can visit the pages below to search problems by company tags. Then come back
 200 | [Number of Islands](https://leetcode.com/problems/number-of-islands/description/) | [Solution](https://github.com/zhubofei/LeetCode-Swift/blob/master/0200-number-of-islands.playground/Contents.swift) | BFS
 259 | [Three Sum Smaller](https://leetcode.com/problems/3sum-smaller/description/) | [Solution](https://github.com/zhubofei/LeetCode-Swift/blob/master/0259-3sum-smaller.playground/Contents.swift) | Two Pointers
 280 | [Wiggle Sort](https://leetcode.com/problems/wiggle-sort/description/) | [Solution](https://github.com/zhubofei/LeetCode-Swift/blob/master/0280-wiggle-sort.playground/Contents.swift) | Swap
+298 | [Binary Tree Longest Consecutive Sequence](https://leetcode.com/problems/binary-tree-longest-consecutive-sequence/description/) | [Solution](https://github.com/zhubofei/LeetCode-Swift/blob/master/0298-binary-tree-longest-consecutive-sequence.playground/Contents.swift) | DFS
 482 | [License Key Formatting](https://leetcode.com/problems/license-key-formatting/description/) | [Solution](https://github.com/zhubofei/LeetCode-Swift/blob/master/0482-license-key-formatting.playground/Contents.swift) | String
 681 | [Next Closest Time](https://leetcode.com/problems/next-closest-time/description/) | [Solution](https://github.com/zhubofei/LeetCode-Swift/blob/master/0681-next-closest-time.playground/Contents.swift) | Simulation
 683 | [K Empty Slots](https://leetcode.com/problems/k-empty-slots/description/) | [Solution](https://github.com/zhubofei/LeetCode-Swift/blob/master/0683-k-empty-slots.playground/Contents.swift) | Sliding Window