pair <int, struct Node*> findLCA(struct Node* root, int n1, int n2)
{
// Base case
if (root == NULL) return make_pair(-1,NULL);
// If either n1 or n2 matches with root's key, report
// the presence by returning root (Note that if a key is
// ancestor of other, then the ancestor key becomes LCA
if (root->key == n1 || root->key == n2)
return make_pair(1,root);
// Look for keys in left and right subtrees
pair <int, struct Node*> left_lca = findLCA(root->left, n1, n2);
pair <int, struct Node*> right_lca = findLCA(root->right, n1, n2);
// If both of the above calls return Non-NULL, then one key
// is present in once subtree and other is present in other,
// So this node is the LCA
if (left_lca.second && right_lca.second ){
if( left_lca.first == right_lca.first && right_lca.first!=1)
//return benar
return make_pair(left_lca.first+1,left_lca);
}
// Otherwise check if left subtree or right subtree is LCA
return (left_lca != /*ga ketemu*/) ?
//naik ke atas
make_pair(left_lca.first + 1, left_lca.second ):
make_pair(right_lca+1,right_lca.second );
}
tree_node *findLCA(tree_node *root, tree_node *node1, tree_node *node2){
if(root == NULL) return NULL;
if(root == node1 || root == node2) return root;
tree_node *left = findLCA(root->left, node1, node2);
tree_node *right = findLCA(root->right, node1, node2);
if(left && right) return root;
else return (left != NULL ? left : right);
}
struct tree *findLCA(struct tree * root, int a, int b)
{
if(root==NULL) return NULL;
if(root->data==a || root->data==b)return root;
struct tree *left=findLCA(root->left,a,b);
struct tree *right=findLCA(root->right,a,b);
if( left && right) return root;
return left?left:right;
}
int main(){
node * root = newNode(1);
root->left = newNode(2);
root->right = newNode(3);
root->left->left = newNode(4);
root->left->right = newNode(5);
root->right->left = newNode(6);
root->right->right = newNode(7);
cout << "LCA(4, 5) = " << findLCA(root, 4, 5);
cout << "\nLCA(4, 6) = " << findLCA(root, 4, 6);
cout << "\nLCA(3, 4) = " << findLCA(root, 3, 4);
cout << "\nLCA(2, 4) = " << findLCA(root, 4, 2);
return 0;
}
//使用递归的方法查找lca，如果结点的左子树与右子树分别包含n1与n2，那么此结点就是lca
//否则lca在子结点中，继续递归进行查找。
BinaryNode* findLCA(BinaryNode *root, int n1, int n2){
if (root->val == n1 || root->val == n2) {
return root;
}
BinaryNode *leftLca = findLCA(root->left, n1, n2);
BinaryNode *rightLca = findLCA(root->right, n1, n2);
if (leftLca && rightLca) {
return root;
}
return leftLca ? leftLca : rightLca;
}
bool findArgument(int s)
{
bool ret = 0;
memset(tag, 0, sizeof(tag));
memset(fa, 0, sizeof(fa));
for (int i = 1; i <= n; i++) f[i] = i;
queue<int> q;
q.push(s);
tag[s] = S;
while (!q.empty())
{
int u = q.front(); q.pop();
for (int v = 1; v <= n; v++) if (G[u][v] && v != matched[u] && find(u) != find(v) && tag[v] != T)
{
if (tag[v] == S) // meet a S node
{
int p = findLCA(u, v);
// important
if (find(u) != p) fa[u] = v;
if (find(v) != p) fa[v] = u;
// important order
contract(u, p, q);
contract(v, p, q);
}
else if (!matched[v]) // find a free node
{
argument(u, v);
return 1;
}
else // find a matched node
expand(u, v, q);
}
}
return 0;
}
//计算两个结点距离
int calDistance(BinaryNode *root, int n1, int n2){
BinaryNode *lca = findLCA(root, n1, n2);
int dst1 = calDis(lca, n1);
int dst2 = calDis(lca, n2);
return dst1 + dst2;
}
bool LCA::test() {
vector<int> preOrder1 = {314, 6, BTNULL, 2, BTNULL, 3, BTNULL, BTNULL, 6, 2, 3};
size_t pos = 0;
unique_ptr<BinaryTreeNode<int>> root1 = createPreOrderIntBTree(preOrder1, &pos);
unique_ptr<BinaryTreeNode<int>> &node11 = root1.get()->left;
unique_ptr<BinaryTreeNode<int>> &node12 = root1.get()->right;
if (findLCA(node11, node12)->data != 314) {
cout << "root1 should be common ancestor" << endl;
return false;
}
return true;
}
struct node *findLCA(struct node* root, int n1, int n2)
{
// Base case
if (root == NULL) return NULL;
// If either n1 or n2 matches with root's data, report
// the presence by returning root (Note that if a data is
// ancestor of other, then the ancestor data becomes LCA
if (root->data == n1 || root->data == n2)
return root;
// Look for datas in left and right subtrees
struct node *left_lca = findLCA(root->left, n1, n2);
struct node *right_lca = findLCA(root->right, n1, n2);
// If both of the above calls return Non-NULL, then one data
// is present in once subtree and other is present in other,
// So this node is the LCA
if (left_lca && right_lca) return root;
// Otherwise check if left subtree or right subtree is LCA
return (left_lca != NULL)? left_lca: right_lca;
}
bool FindLCA::test() {
vector<int> preOrder = {19, 7, 3, 2, 5, 11, 17, 13, 43, 23, 37, 29, 31, 41, 47, 53};
unique_ptr<BSTNode<int>> tree = createBSTFromPreorder(preOrder);
unique_ptr<BSTNode<int>> &c = tree.get()->left.get()->left;
unique_ptr<BSTNode<int>> &g = tree.get()->left.get()->right.get()->right;
int ans = 7;
BSTNode<int> *res = findLCA(tree, c, g);
if (res->data != ans) {
cout << "Should be " << ans << endl;
cout << "Result " << res->data << endl;
return false;
}
return true;
}
