From 02fd6b8f9a9dc49af1612762c80a439e0a1f5e04 Mon Sep 17 00:00:00 2001 From: YDLIN <1924723909@qq.com> Date: Fri, 21 Jan 2022 10:45:10 +0800 Subject: [PATCH 1/5] =?UTF-8?q?=E6=B7=BB=E5=8A=A0257.=20=E4=BA=8C=E5=8F=89?= =?UTF-8?q?=E6=A0=91=E7=9A=84=E6=89=80=E6=9C=89=E8=B7=AF=E5=BE=84=20Swift?= =?UTF-8?q?=20=E7=89=88=E6=9C=AC?= MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit --- problems/0257.二叉树的所有路径.md | 91 +++++++++++++++++++++++ 1 file changed, 91 insertions(+) diff --git a/problems/0257.二叉树的所有路径.md b/problems/0257.二叉树的所有路径.md index cb837d87..9ccd81d8 100644 --- a/problems/0257.二叉树的所有路径.md +++ b/problems/0257.二叉树的所有路径.md @@ -581,6 +581,97 @@ var binaryTreePaths = function(root) { }; ``` +Swift: + +递归法： + +```swift +func binaryTreePaths(_ root: TreeNode?) -> [String] { + var result = Array() + var path = Array() + guard let root = root else { + return result + } + traversal(root, &path, &result) + return result + } + + func traversal(_ cur: TreeNode, _ path: inout Array, _ result: inout Array) { + path.append(cur.val) + // 递归终止条件：到达叶子节点 + if cur.left == nil && cur.right == nil { + var pathString = "" + // 处理 path 前面的元素 + for i in 0.. [String] { + // 保存树的遍历节点 + var treeStack = [TreeNode]() + // 保存遍历路径的节点 + var pathStack = [String]() + // 保存最终路径集合 + var result = [String]() + guard let root = root else { + return result + } + treeStack.append(root) + pathStack.append(String(root.val)) + while !treeStack.isEmpty { + let node = treeStack.removeLast() + let path = pathStack.removeLast() + + // 遇到叶子节点 + if node.left == nil && node.right == nil { + result.append(path) + } + + if let rightNode = node.right { + treeStack.append(rightNode) + let tmp = path + "->" + String(rightNode.val) + pathStack.append(tmp) + } + + if let leftNode = node.left { + treeStack.append(leftNode) + let tmp = path + "->" + String(leftNode.val) + pathStack.append(tmp) + } + } + + return result + } +``` + ----------------------- From 2ec4867125e60381b9ded470a59ad89d0b8401d1 Mon Sep 17 00:00:00 2001 From: YDLIN <1924723909@qq.com> Date: Sat, 22 Jan 2022 10:26:18 +0800 Subject: [PATCH 2/5] =?UTF-8?q?=E6=B7=BB=E5=8A=A0=20404.=20=E5=B7=A6?= =?UTF-8?q?=E5=8F=B6=E5=AD=90=E4=B9=8B=E5=92=8C=20Swift=20=E7=89=88?= =?UTF-8?q?=E6=9C=AC?= MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit --- problems/0404.左叶子之和.md | 48 ++++++++++++++++++++++++++++++++ 1 file changed, 48 insertions(+) diff --git a/problems/0404.左叶子之和.md b/problems/0404.左叶子之和.md index ddbd100e..09272052 100644 --- a/problems/0404.左叶子之和.md +++ b/problems/0404.左叶子之和.md @@ -373,6 +373,54 @@ var sumOfLeftLeaves = function(root) { ``` +## Swift + +**递归法** +```swift +func sumOfLeftLeaves(_ root: TreeNode?) -> Int { + guard let root = root else { + return 0 + } + + let leftValue = sumOfLeftLeaves(root.left) + let rightValue = sumOfLeftLeaves(root.right) + + var midValue: Int = 0 + if root.left != nil && root.left?.left == nil && root.left?.right == nil { + midValue = root.left!.val + } + + let sum = midValue + leftValue + rightValue + return sum +} +``` +**迭代法** +```swift +func sumOfLeftLeaves(_ root: TreeNode?) -> Int { + guard let root = root else { + return 0 + } + + var stack = Array() + stack.append(root) + var sum = 0 + + while !stack.isEmpty { + let lastNode = stack.removeLast() + + if lastNode.left != nil && lastNode.left?.left == nil && lastNode.left?.right == nil { + sum += lastNode.left!.val + } + if let right = lastNode.right { + stack.append(right) + } + if let left = lastNode.left { + stack.append(left) + } + } + return sum +} +``` From 26c7fd202afc2aac492c2db589a3c4af5af3fcf3 Mon Sep 17 00:00:00 2001 From: YDLIN <1924723909@qq.com> Date: Sat, 22 Jan 2022 11:38:28 +0800 Subject: [PATCH 3/5] =?UTF-8?q?=E6=B7=BB=E5=8A=A0=20513.=20=E6=89=BE?= =?UTF-8?q?=E6=A0=91=E5=B7=A6=E4=B8=8B=E8=A7=92=E7=9A=84=E5=80=BC=20Swift?= =?UTF-8?q?=20=E7=89=88=E6=9C=AC?= MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit --- problems/0513.找树左下角的值.md | 68 ++++++++++++++++++++++++++ 1 file changed, 68 insertions(+) diff --git a/problems/0513.找树左下角的值.md b/problems/0513.找树左下角的值.md index 99f42d34..84ed3932 100644 --- a/problems/0513.找树左下角的值.md +++ b/problems/0513.找树左下角的值.md @@ -433,6 +433,74 @@ var findBottomLeftValue = function(root) { }; ``` +## Swift + +递归版本： + +```swift +var maxLen = -1 +var maxLeftValue = 0 +func findBottomLeftValue_2(_ root: TreeNode?) -> Int { + traversal(root, 0) + return maxLeftValue +} + +func traversal(_ root: TreeNode?, _ deep: Int) { + guard let root = root else { + return + } + + if root.left == nil && root.right == nil { + if deep > maxLen { + maxLen = deep + maxLeftValue = root.val + } + return + } + + if root.left != nil { + traversal(root.left, deep + 1) + } + + if root.right != nil { + traversal(root.right, deep + 1) + } + return +} +``` +层序遍历： + +```swift +func findBottomLeftValue(_ root: TreeNode?) -> Int { + guard let root = root else { + return 0 + } + + var queue = [root] + var result = 0 + + while !queue.isEmpty { + let size = queue.count + for i in 0.. Date: Mon, 24 Jan 2022 11:36:06 +0800 Subject: [PATCH 4/5] =?UTF-8?q?=E6=B7=BB=E5=8A=A0=200112.=E8=B7=AF?= =?UTF-8?q?=E5=BE=84=E6=80=BB=E5=92=8C=E3=80=810113.=E8=B7=AF=E5=BE=84?= =?UTF-8?q?=E6=80=BB=E5=92=8C=20II=20Swift=20=E7=89=88=E6=9C=AC?= MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit --- problems/0112.路径总和.md | 117 ++++++++++++++++++++++++++++++++++ 1 file changed, 117 insertions(+) diff --git a/problems/0112.路径总和.md b/problems/0112.路径总和.md index 910e57c8..5ec8ffd0 100644 --- a/problems/0112.路径总和.md +++ b/problems/0112.路径总和.md @@ -766,7 +766,124 @@ let pathSum = function(root, targetSum) { }; ``` +## Swift +0112.路径总和 + +**递归** +```swift +func hasPathSum(_ root: TreeNode?, _ targetSum: Int) -> Bool { + guard let root = root else { + return false + } + + return traversal(root, targetSum - root.val) +} + +func traversal(_ cur: TreeNode?, _ count: Int) -> Bool { + if cur?.left == nil && cur?.right == nil && count == 0 { + return true + } + + if cur?.left == nil && cur?.right == nil { + return false + } + + if let leftNode = cur?.left { + if traversal(leftNode, count - leftNode.val) { + return true + } + } + + if let rightNode = cur?.right { + if traversal(rightNode, count - rightNode.val) { + return true + } + } + + return false +} +``` +**迭代** +```swift +func hasPathSum(_ root: TreeNode?, _ targetSum: Int) -> Bool { + guard let root = root else { + return false + } + + var stack = Array<(TreeNode, Int)>() + stack.append((root, root.val)) + + while !stack.isEmpty { + let node = stack.removeLast() + + if node.0.left == nil && node.0.right == nil && targetSum == node.1 { + return true + } + + if let rightNode = node.0.right { + stack.append((rightNode, node.1 + rightNode.val)) + } + + if let leftNode = node.0.left { + stack.append((leftNode, node.1 + leftNode.val)) + } + } + + return false +} +``` + +0113.路径总和 II + +**递归** + +```swift +var result = [[Int]]() +var path = [Int]() +func pathSum(_ root: TreeNode?, _ targetSum: Int) -> [[Int]] { + result.removeAll() + path.removeAll() + guard let root = root else { + return result + } + path.append(root.val) + traversal(root, count: targetSum - root.val) + return result + +} + +func traversal(_ cur: TreeNode?, count: Int) { + var count = count + // 遇到了叶子节点且找到了和为targetSum的路径 + if cur?.left == nil && cur?.right == nil && count == 0 { + result.append(path) + return + } + + // 遇到叶子节点而没有找到合适的边，直接返回 + if cur?.left == nil && cur?.right == nil{ + return + } + + if let leftNode = cur?.left { + path.append(leftNode.val) + count -= leftNode.val + traversal(leftNode, count: count)// 递归 + count += leftNode.val// 回溯 + path.removeLast()// 回溯 + } + + if let rightNode = cur?.right { + path.append(rightNode.val) + count -= rightNode.val + traversal(rightNode, count: count)// 递归 + count += rightNode.val// 回溯 + path.removeLast()// 回溯 + } + return +} +``` From 9272063cf2627a6334cea807cd3de2e7166da1af Mon Sep 17 00:00:00 2001 From: YDLIN <1924723909@qq.com> Date: Mon, 24 Jan 2022 16:42:47 +0800 Subject: [PATCH 5/5] =?UTF-8?q?=E6=B7=BB=E5=8A=A0=200654.=20=E6=9C=80?= =?UTF-8?q?=E5=A4=A7=E4=BA=8C=E5=8F=89=E6=A0=91=20Swift=20=E7=89=88?= =?UTF-8?q?=E6=9C=AC?= MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit --- problems/0654.最大二叉树.md | 27 +++++++++++++++++++++++++++ 1 file changed, 27 insertions(+) diff --git a/problems/0654.最大二叉树.md b/problems/0654.最大二叉树.md index b4679c7d..44c74f89 100644 --- a/problems/0654.最大二叉树.md +++ b/problems/0654.最大二叉树.md @@ -401,6 +401,33 @@ struct TreeNode* constructMaximumBinaryTree(int* nums, int numsSize){ } ``` +## Swift +```swift +func constructMaximumBinaryTree(_ nums: inout [Int]) -> TreeNode? { + return traversal(&nums, 0, nums.count) +} + +func traversal(_ nums: inout [Int], _ left: Int, _ right: Int) -> TreeNode? { + if left >= right { + return nil + } + + var maxValueIndex = left + for i in (left + 1).. nums[maxValueIndex] { + maxValueIndex = i + } + } + + let root = TreeNode(nums[maxValueIndex]) + + root.left = traversal(&nums, left, maxValueIndex) + root.right = traversal(&nums, maxValueIndex + 1, right) + return root +} +``` + + -----------------------