TreeNode* constructFromPrePost(vector<int>& pre, vector<int>& post) {
if(pre.size()==0) return NULL;
TreeNode *root = new TreeNode(*(pre.begin()));
if(pre.size()==1){
return root;
}
else if(pre.size()==2){
(root->left) = new TreeNode(pre[1]);
return root;
}
else if(pre.size()==3){
if(pre[1]==post[0])
{
(root->left) = new TreeNode(pre[1]);
(root->right) = new TreeNode(pre[2]);
}
else{
(root->left) = new TreeNode(pre[1]);
(root->left)->left = new TreeNode(pre[2]);
}
return root;
}
vector<int> t_vecpre;
vector<int> t_vecpost;
FindVector(pre,post,pre[1],t_vecpre,t_vecpost);
root->left = constructFromPrePost(t_vecpre,t_vecpost);
cout<<"------------"<<endl;
Display(pre);
Display(post);
t_vecpre.clear();
t_vecpost.clear();
if(pre.size()<=1) {
root->right = NULL;
}
else{
FindVector(pre,post,pre[1],t_vecpre,t_vecpost);
root->right = constructFromPrePost(t_vecpre,t_vecpost);
}
return root;
}
TreeNode* constructFromPrePost(int preLeft, int preRight, vector<int>& preOrder,
int postLeft, int postRight, vector<int>& postOrder) {
if(preLeft > preRight) {
return nullptr;
}
TreeNode* root = new TreeNode(preOrder[preLeft]);
if(preLeft == preRight) {
return root;
}
int pivot = -1;
for(int i = preLeft + 1; i <= preRight; i++) {
if(preOrder[i] == postOrder[postRight - 1]) {
pivot = i;
break;
}
}
root->left = constructFromPrePost(preLeft + 1, pivot - 1, preOrder,
postLeft, postLeft + pivot - 1 - preLeft - 1, postOrder);
root->right = constructFromPrePost(pivot, preRight, preOrder,
postRight - 1 - preRight + pivot, postRight - 1, postOrder);
return root;
}
TreeNode *Solution889::constructFromPrePost(vector<int> &pre, vector<int> &post)
{
TreeNode *root = nullptr;
unsigned long len = pre.size();
if (len == 0)
return root;
root = new TreeNode(pre[0]);
if (len == 1)
return root;
int leftChild = pre[1];
// Only One Child
if (leftChild == post[len - 2])
{
vector<int> leftPre = vector<int>(pre.begin() + 1, pre.end());
vector<int> leftPost = vector<int>(post.begin(), post.begin() + len - 1);
root->left = constructFromPrePost(leftPre, leftPost);
}
else // Two Children
{
auto leftChildPosInPost = len - 2;
for (; leftChildPosInPost >= 0; --leftChildPosInPost)
{
if (post[leftChildPosInPost] == pre[1])
break;
}
vector<int> leftPre = vector<int>(pre.begin() + 1, pre.begin() + 1 + (leftChildPosInPost + 1));
vector<int> leftPost = vector<int>(post.begin(), post.begin() + (leftChildPosInPost + 1));
vector<int> rightPre = vector<int>(pre.begin() + 1 + (leftChildPosInPost + 1), pre.end());
vector<int> rightPost = vector<int>(post.begin() + (leftChildPosInPost + 1), post.end() - 1);
root->left = constructFromPrePost(leftPre, leftPost);
root->right = constructFromPrePost(rightPre, rightPost);
}
return root;
}
TreeNode* constructFromPrePost(vector<int>& pre, vector<int>& post) {
return constructFromPrePost(0, pre.size() - 1, pre, 0, post.size() - 1, post);
}
