feat: add swift implementation to lcof2 problem: No.050 (doocs#3065)

klever34 · web-flow · commit e546aabf3b25 · 2024-06-07T17:43:33.000+08:00
diff --git a/lcof2/剑指 Offer II 050. 向下的路径节点之和/README.md b/lcof2/剑指 Offer II 050. 向下的路径节点之和/README.md
@@ -241,6 +241,57 @@ function pathSum(root: TreeNode | null, targetSum: number): number {
 }
 ```
 
+#### Swift
+
+```swift
+/* class TreeNode {
+*     var val: Int
+*     var left: TreeNode?
+*     var right: TreeNode?
+*     init() {
+*         self.val = 0
+*         self.left = nil
+*         self.right = nil
+*     }
+*     init(_ val: Int) {
+*         self.val = val
+*         self.left = nil
+*         self.right = nil
+*     }
+*     init(_ val: Int, _ left: TreeNode?, _ right: TreeNode?) {
+*         self.val = val
+*         self.left = left
+*         self.right = right
+*     }
+* }
+*/
+
+class Solution {
+    private var cnt = [Int: Int]()
+    private var targetSum: Int = 0
+
+    func pathSum(_ root: TreeNode?, _ targetSum: Int) -> Int {
+        self.targetSum = targetSum
+        cnt[0] = 1
+        return dfs(root, 0)
+    }
+
+    private func dfs(_ node: TreeNode?, _ s: Int) -> Int {
+        guard let node = node else {
+            return 0
+        }
+        var s = s
+        s += node.val
+        var ans = cnt[s - targetSum, default: 0]
+        cnt[s, default: 0] += 1
+        ans += dfs(node.left, s)
+        ans += dfs(node.right, s)
+        cnt[s]! -= 1
+        return ans
+    }
+}
+```
+
 <!-- tabs:end -->
 
 <!-- solution:end -->
diff --git a/lcof2/剑指 Offer II 050. 向下的路径节点之和/Solution.swift b/lcof2/剑指 Offer II 050. 向下的路径节点之和/Solution.swift
@@ -0,0 +1,46 @@
+/* class TreeNode {
+*     var val: Int
+*     var left: TreeNode?
+*     var right: TreeNode?
+*     init() {
+*         self.val = 0
+*         self.left = nil
+*         self.right = nil
+*     }
+*     init(_ val: Int) {
+*         self.val = val
+*         self.left = nil
+*         self.right = nil
+*     }
+*     init(_ val: Int, _ left: TreeNode?, _ right: TreeNode?) {
+*         self.val = val
+*         self.left = left
+*         self.right = right
+*     }
+* }
+*/
+
+class Solution {
+    private var cnt = [Int: Int]()
+    private var targetSum: Int = 0
+
+    func pathSum(_ root: TreeNode?, _ targetSum: Int) -> Int {
+        self.targetSum = targetSum
+        cnt[0] = 1
+        return dfs(root, 0)
+    }
+
+    private func dfs(_ node: TreeNode?, _ s: Int) -> Int {
+        guard let node = node else {
+            return 0
+        }
+        var s = s
+        s += node.val
+        var ans = cnt[s - targetSum, default: 0]
+        cnt[s, default: 0] += 1
+        ans += dfs(node.left, s)
+        ans += dfs(node.right, s)
+        cnt[s]! -= 1
+        return ans
+    }
+}
