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Given two non-empty binary trees s and t, check whether tree t has exactly the same structure and node values with a subtree of s. A subtree of s is a tree consists of a node in s and all of this node's descendants. The tree s could also be considered as a subtree of itself.
Example 1:
Given tree s:
3
/
4 5
/
1 2
Given tree t:
4 / 1 2
Return true, because t has the same structure and node values with a subtree of s.
Example 2:
Given tree s:
3
/
4 5
/
1 2
/
0
Given tree t:
4 / 1 2
Return false.
给定两个非空二叉树 s 和 t，检验 s 中是否包含和 t 具有相同结构和节点值的子树。s 的一个子树包括 s 的一个节点和这个节点的所有子孙。s 也可以看做它自身的一棵子树。
示例 1:
给定的树 s:
3
/
4 5
/
1 2
给定的树 t：
4 / 1 2
返回 true，因为 t 与 s 的一个子树拥有相同的结构和节点值。
示例 2:
给定的树 s：
3
/
4 5
/
1 2
/
0
给定的树 t：
4 / 1 2
返回 false。
376ms
1 /** 2 * Definition for a binary tree node. 3 * public class TreeNode { 4 * public var val: Int 5 * public var left: TreeNode? 6 * public var right: TreeNode? 7 * public init(_ val: Int) { 8 * self.val = val 9 * self.left = nil 10 * self.right = nil 11 * } 12 * } 13 */ 14 class Solution { 15 func isSubtree(_ s: TreeNode?, _ t: TreeNode?) -> Bool { 16 if s == nil || t == nil {return false} 17 return isSameTree(s,t) || isSubtree(s?.left,t) || isSubtree(s?.right,t) 18 } 19 func isSameTree(_ p: TreeNode?, _ q: TreeNode?) -> Bool 20 { 21 if p == nil 22 { 23 if q == nil 24 { 25 return true 26 } 27 return false 28 } 29 else if q == nil 30 { 31 return false 32 } 33 return p?.val == q?.val 34 && isSameTree(p?.left, q?.left) 35 && isSameTree(p?.right, q?.right) 36 } 37 38 }
120ms
1 /** 2 * Definition for a binary tree node. 3 * public class TreeNode { 4 * public var val: Int 5 * public var left: TreeNode? 6 * public var right: TreeNode? 7 * public init(_ val: Int) { 8 * self.val = val 9 * self.left = nil 10 * self.right = nil 11 * } 12 * } 13 */ 14 class Solution { 15 func isSameTree(_ s: TreeNode?, _ t: TreeNode?) -> Bool { 16 if (s == nil && t != nil) || (s != nil && t == nil) { 17 return false 18 } 19 20 if s == nil && t == nil { 21 return true 22 } 23 24 if s!.val != t!.val { 25 return false 26 } 27 28 return isSubtree(s?.left, t?.left) && isSubtree(s?.right, t?.right) 29 } 30 31 func getSuitableNode(_ s: TreeNode?, _ dest: Int, _ result: inout [TreeNode?]) -> Int { 32 guard let s = s else { 33 return -1 34 } 35 36 let depth = max(getSuitableNode(s.left, dest, &result), getSuitableNode(s.right, dest, &result)) + 1 37 if depth == dest { 38 result.append(s) 39 } 40 41 return depth 42 } 43 44 func isSubtree(_ s: TreeNode?, _ t: TreeNode?) -> Bool { 45 if s == nil && t == nil { 46 return true 47 } 48 49 if s == nil || t == nil { 50 return false 51 } 52 53 var nodes = [TreeNode?]() 54 let depth = getSuitableNode(t, -1, &nodes) 55 56 getSuitableNode(s, depth, &nodes) 57 58 for node in nodes { 59 if isSameTree(node, t) { 60 return true 61 } 62 } 63 64 return false 65 } 66 }
124ms
1 /** 2 * Definition for a binary tree node. 3 * public class TreeNode { 4 * public var val: Int 5 * public var left: TreeNode? 6 * public var right: TreeNode? 7 * public init(_ val: Int) { 8 * self.val = val 9 * self.left = nil 10 * self.right = nil 11 * } 12 * } 13 */ 14 class Solution { 15 func isSubtree(_ s: TreeNode?, _ t: TreeNode?) -> Bool { 16 let S = getString(s) 17 let T = getString(t) 18 19 return S.contains(T) 20 } 21 22 func getString(_ n: TreeNode?) -> String { 23 guard let n = n else { return "nil" } 24 25 return "#" + String(n.val) + getString(n.left) + getString(n.right) 26 } 27 }
164ms
1 class Solution { 2 func isSubtree(_ s: TreeNode?, _ t: TreeNode?) -> Bool { 3 guard let t = t else { 4 return s == nil 5 } 6 7 if let s = s { 8 if s.val == t.val { 9 return isSameTree(s,t) || isSubtree(s.left,t) || isSubtree(s.right,t) 10 } else { 11 return isSubtree(s.left,t) || isSubtree(s.right,t) 12 } 13 } 14 return false 15 } 16 17 func isSameTree(_ s:TreeNode?, _ t:TreeNode?) -> Bool { 18 guard let _s = s, let _t = t else { 19 return s == nil && t == nil 20 } 21 if _s.val != _t.val { 22 return false 23 } 24 25 return isSameTree(_s.left,_t.left) && isSameTree(_s.right,_t.right) 26 } 27 }
180ms
1 /** 2 * Definition for a binary tree node. 3 * public class TreeNode { 4 * public var val: Int 5 * public var left: TreeNode? 6 * public var right: TreeNode? 7 * public init(_ val: Int) { 8 * self.val = val 9 * self.left = nil 10 * self.right = nil 11 * } 12 * } 13 */ 14 class Solution { 15 func isSubtree(_ s: TreeNode?, _ t: TreeNode?) -> Bool { 16 guard let s = s else { 17 return t == nil 18 } 19 20 guard let t = t else { 21 return true 22 } 23 24 let left = isSubtree(s.left, t) 25 let right = isSubtree(s.right, t) 26 return left || right || isSameTree(s, t) 27 } 28 29 fileprivate func isSameTree(_ s: TreeNode?, _ t: TreeNode?) -> Bool { 30 31 guard let s = s else { 32 return t == nil 33 } 34 35 guard let t = t else { 36 return false 37 } 38 39 let left = isSameTree(s.left, t.left) 40 let right = isSameTree(s.right, t.right) 41 return s.val == t.val && left && right 42 } 43 }