preorder tree construction

puzzles/interviews/training/preorder_tree_construction.cpp

@@ -0,0 +1,102 @@
+#include <vector>
+#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 * prefix_to_tree( const std::vector<double>& v ){
+    
+    if ( !v.size() ){
+        return nullptr;
+    }
+
+    node * root = new node(v[0]);
+    node * current = root;
+    node * max_node = nullptr;
+
+    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;                    
+                }
+            }
+        } else {
+            std::cout << "error" << std::endl;
+            break;
+        }
+
+        if ( !current || !root ) {
+            std::cout << "errrrrrror" << std::endl;
+        }
+    }
+
+    std::cout << root << std::endl;
+    return root;
+}
+
+void print( node * root, const std::string& level = "" ){
+    if ( root ) {
+        print( root->left, level + "   ");
+        std::cout << level << "- " << root->data << std::endl;
+        print( root->right, level + "   ");
+    }
+}
+
+void traverse( node * root, std::vector<double>& v ){
+    if ( root ) {
+        v.push_back(root->data);
+        traverse(root->left, v);
+        traverse(root->right, v);
+    }
+}
+
+void test( const std::vector<double>& v ){
+    auto r = prefix_to_tree( v );
+    //print( r );
+    std::vector<double> w;
+    traverse( r, w );
+    if ( v.size() != w.size() ) {
+        std::cout << "v.size() != w.size() => " << v.size() << " != " << w.size() << std::endl;
+    }
+    for (int i = 0; i < v.size(); ++i ){
+        if (v[i]!=w[i]){
+            std::cout << "error at index " << i << " -> "<< v[i] << " != " << w[i] << std::endl;
+        }
+    }
+}
+
+int main( void ) {
+
+    test( {1} );
+    test( {2, 1, 3} );
+    test( {4, 2, 1, 3, 6, 5, 7} );
+    test( {8, 4, 2, 1, 3, 6, 5, 7, 12, 10, 9, 11, 14, 13, 15} );
+    test( {8, 4, 2,    3, 6, 5, 7, 12, 10, 9, 11, 14, 13, 15} );
+    test( {8, 4,          6, 5, 7, 12, 10, 9,     14, 13, 15} );
+    test( {8,                      12, 10, 9, 11, 14, 13,   } );
+    test( {8, 4, 2, 1,    6,       12, 10,    11, 14,     15} );
+
+    return 0;
+}