#### 1.introduction↵
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As everyone knows, my friend [user:Billy2007,2020-04-16] is not good at The algorithm of tree, So I and he write this blog.↵
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LCA , that is, the recent Common ancestor, refers to the root tree, find out one or two nodes u and v recent Common ancestor.↵
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#### 2.how to ask LCA?↵
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For example:↵
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Given a tree with multiple branches, the public ancestor that is closest to the specified two points is requested.↵
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The first line contains three positive integers,$$$N,M,S$$$ which respectively represent the number of nodes in the tree, the number of inquiries, and the number of root nodes.↵
Next, n-1n-1 rows each contain two positive integers x, yx,y, indicating that there is a directly connected edge between xx node and yy node (the data is guaranteed to form a tree).↵
Next, MM rows each contain two positive integers a, ba, and b, which means that the nearest common ancestor of aa and bb is inquired.
↵
As everyone knows, my friend [user:Billy2007,2020-04-16] is not good at The algorithm of tree, So I and he write this blog.↵
↵
LCA , that is, the recent Common ancestor, refers to the root tree, find out one or two nodes u and v recent Common ancestor.↵
↵
#### 2.how to ask LCA?↵
↵
For example:↵
↵
Given a tree with multiple branches, the public ancestor that is closest to the specified two points is requested.↵
↵
The first line contains three positive integers,
Next, n-1n-1 rows each contain two positive integers x, yx,y, indicating that there is a directly connected edge between xx node and yy node (the data is guaranteed to form a tree).↵
Next, MM rows each contain two positive integers a, ba, and b, which means that the nearest common ancestor of aa and bb is inquired.
