LCA后代节点

LCA descendant nodes

本文关键字：节点 后代 LCA      更新时间：2023-10-16

我试图获得树中两个节点的最小共同祖先。我试过了，但问题是if one node is the descendant node for other我无法得到LCA。
我试着解决它，然后它只适用于后代节点。我不知道该怎么做。

Node* Tree::LCA(Node* root, Node* n1, Node* n2) {
    list<Node*> a1,a2;
    while(n1 != NULL) {
        a1.push_back(n1->parent);
        n1 = n1->parent;
    }
    while(n2 != NULL) {
        a2.push_back(n2->parent);
        n2 = n2->parent;
    }
    while(!a1.empty() && !a2.empty() && a1.back() == a2.back()) {   
        a1.pop_back();
        a2.pop_back();
    }
    if( a1.back() != a2.back()) {
        Node* rn = a1.back();
        cout << " LCA of r-U and r_v is " << rn->index << endl;
    }
}

从n1->parent和n2->parent开始推。相反，在推他们的父母和其他祖先之前，也推n1和n2。所以你的代码应该是:

Node* Tree::LCA(Node* root, Node* n1, Node* n2) {
    list<Node*> a1,a2;
    a1.push_back(n1); // line to be added
    while(n1 != NULL) {
        a1.push_back(n1->parent);
        n1 = n1->parent;
    }
    a2.push_back(n2); // line to be added
    while(n2 != NULL) {
        a2.push_back(n2->parent);
        n2 = n2->parent;
    }
    // rest of code

Node* Tree::LCA(Node* root, Node* n1, Node* n2) {
    list<Node*> a1,a2;
    while(n1 != NULL) {
        a1.push_back(n1); // push n1 
        n1 = n1->parent;
    }
    while(n2 != NULL) {
        a2.push_back(n2);  // push n2
        n2 = n2->parent;
    }
    Node* old; // create new node
    while(!a1.empty() && !a2.empty() && a1.back() == a2.back()) {
        old = a1.back(); // store the node before popping
        a1.pop_back();
        a2.pop_back();
    }
    if( a1.back() != a2.back()) {
       // Node* rn = a1.back();  //not needed
        cout << " LCA of r-U and r_v is " << old->index << endl; // changed 
    }
}
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