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preorder tree construction: much better algorithm. No need to keep root.

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This commit is contained in:
Vahagn Khachatryan
2018-02-04 10:40:31 +00:00
parent 08e93603a9
commit cdfa46e84c
1 changed files with 19 additions and 29 deletions
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48
puzzles/interviews/training/preorder_tree_construction.cpp
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@@ -5,17 +5,16 @@ VIM: let b:argv=""
*/
#include <vector>
#include <string>
#include <stack>
#include <iostream>
struct node {
node * root = nullptr;
node * left = nullptr;
node * right = nullptr;
double data = 0;
node( double d, node * r = nullptr )
: root(r)
, data(d)
node( double d )
: data(d)
{}
};
@@ -26,35 +25,26 @@ node * prefix_to_tree( const std::vector<double>& v ){
}
node * root = new node(v[0]);
node * current = root;
node * max_node = nullptr;
std::stack<node*> stack;
stack.push(root);
for ( int i = 1; i < v.size(); ) {
if ( v[i] < current->data ){
max_node = current;
current = new node(v[i++],current);
current->root->left = current;
} else if ( !max_node
|| v[i] < max_node->data ){
current = new node(v[i++],current);
current->root->right = current;
} else if ( current->root ){
current = current->root;
while ( max_node
&& max_node->data <= current->data ) {
node * tmp = max_node;
max_node = max_node->root;
if ( max_node && tmp == max_node->left ){
break;
}
}
if ( v[i] < stack.top()->data ){
auto n = new node(v[i++]);
stack.top()->left = n;
stack.push(n);
} else {
std::cout << "error" << std::endl;
break;
}
auto c = stack.top();
stack.pop();
while( !stack.empty() && stack.top()->data < v[i] ){
c = stack.top();
stack.pop();
}
if ( !current || !root ) {
std::cout << "errrrrrror" << std::endl;
auto n = new node(v[i++]);
c->right = n;
stack.push(n);
}
}