653. 两数之和 IV - 输入 BST(bfs)

文章目录

• ​​Question​​
• ​​Ideas​​
• ​​Code​​

Question

​​653. 两数之和 IV - 输入 BST(bfs)​​

Ideas

bfs 用队列模拟 需要一个判重数组 （防止重复走）+ 拓展点

Code

O（N）

# Definition for a binary tree node.
# class TreeNode:
#     def __init__(self, val=0, left=None, right=None):
#         self.val = val
#         self.left = left
#         self.right = right
class Solution:
    def findTarget(self, root: Optional[TreeNode], k: int) -> bool:
        # 遍历二叉树
        def bfs(root):
            if not root:
                return False
            q = [root]
            lis = []
            while q:
                t = q.pop(0) 
                lis.append(t.val)
                if t.left:
                    q.append(t.left)
                if t.right:
                    q.append(t.right)
            n = len(lis)
            map = []
            for i in range(n):
                if lis[i] not in map:
                    # dic[k-lis[i]] = i
                    map.append(k-lis[i])
                else:
                    return True
            return False
        return bfs(root)