236. Lowest Common Ancestor of a Binary Tree
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Given a binary tree, find the lowest common ancestor (LCA) of two given nodes in the tree.
According to the definition of LCA on Wikipedia: “The lowest common ancestor is defined between two nodes v and w as the lowest node in T that has both v and w as descendants (where we allow a node to be a descendant of itself).”
_______3______ / \ ___5__ ___1__ / \ / \ 6 _2 0 8 / \ 7 4
For example, the lowest common ancestor (LCA) of nodes 5
and 1
is 3
. Another example is LCA of nodes 5
and 4
is 5
, since a node can be a descendant of itself according to the LCA definition.
思路:这题有上题不同,这是一颗普通的二叉树,我们可以用分别得到到p,q的两个路径,看两个路径的最接近的就是最低公共祖先
代码如下(已通过leetcode)
public class Solution {
public TreeNode lowestCommonAncestor(TreeNode root, TreeNode p, TreeNode q) {
List<TreeNode> list1=new ArrayList<TreeNode>();
List<TreeNode> list2=new ArrayList<TreeNode>();
getpath(root,p,list1);
getpath(root,q,list2);
for(int i=0;i<=list1.size();i++) {
if(list2.contains(list1.get(i))) return list1.get(i);
}
return null;
}
private boolean getpath(TreeNode root, TreeNode p, List<TreeNode> list) {
// TODO Auto-generated method stub
if(root==null) return false;
if(root==p) {
list.add(root);
return true;
}else {
if(getpath(root.left, p, list)||getpath(root.right, p, list)) {
list.add(root);
return true;
}
return false;
}
}
}
- Lowest Common Ancestor of a Binary Tree
- Lowest Common Ancestor of a Binary Tree
- Lowest Common Ancestor of a Binary Tree
- Lowest Common Ancestor of a Binary Tree
- Lowest Common Ancestor of a Binary Tree
- Lowest Common Ancestor of a Binary Tree
- Lowest Common Ancestor of a Binary Tree
- Lowest Common Ancestor of a Binary Tree
- Lowest Common Ancestor of a Binary Tree
- Lowest Common Ancestor of a Binary Tree(***)
- Lowest Common Ancestor of a Binary Tree
- Lowest Common Ancestor of a Binary Tree
- Lowest Common Ancestor of a Binary Tree
- Lowest Common Ancestor of a Binary Tree
- Lowest Common Ancestor of a Binary Tree
- Lowest Common Ancestor of a Binary Tree
- Lowest Common Ancestor of a Binary Tree
- Lowest Common Ancestor of a Binary Tree
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