delete

tree.cpp

@@ -3,27 +3,64 @@
 #include<vector>
 #include<memory>
 
+template <typename T>
+struct Node;
+
+template <typename T>
+using Node_ptr = std::unique_ptr<Node<T>>;
+
 template <typename T>
 struct Node{
     T value;
-    std::unique_ptr<Node<T>> small;
-    std::unique_ptr<Node<T>> big;
+    Node_ptr<T> small;
+    Node_ptr<T> big;
     void dump(std::ofstream& ofs) const;
 };
 
 template <typename T>
 class Tree{
-    std::unique_ptr<Node<T>> root;
+    Node_ptr<T> root;
+    Node_ptr<T>* find(T val);
+    Node_ptr<T>* find_to_swap(Node_ptr<T>* unwanted);
+
 public:
     bool insert(T val);
-    void del(T val);
-    
+    bool del(T val);
     void print() const;
 };
 
+template <typename T>
+Node_ptr<T>* Tree<T>::find(T val){
+    for(Node_ptr<T>* n = &root; *n;){
+        if(val == (*n)->value) return n;
+        else if(val < (*n)->value) n = &(*n)->small;
+        else n = &(*n)->big;
+    }
+    return nullptr;
+}
 
 template <typename T>
-void del(T val);
+Node_ptr<T>* Tree<T>::find_to_swap(Node_ptr<T>* unwanted){
+    if((*unwanted)->small) unwanted = &(*unwanted)->small;
+    else return nullptr;
+    while((*unwanted)->big) unwanted = &(*unwanted)->big;
+    return unwanted;
+}
+
+template <typename T>
+bool Tree<T>::del(T val){
+    Node_ptr<T>* unwanted = find(val);
+    if(!unwanted) return false;
+    Node_ptr<T>* to_swap = find_to_swap(unwanted);
+    if(!to_swap){
+        (*unwanted).reset((*unwanted)->big.release());
+    }
+    else{
+        std::swap((*unwanted)->value, (*to_swap)->value);
+        (*to_swap).reset((*to_swap)->small.release());
+    }
+    return true;
+}
 
 template <typename T>
 bool Tree<T>::insert(T val){
@@ -83,12 +120,15 @@ void Tree<T>::print() const {
 
 int main(){
     Tree<int> t;
-    std::vector<int> v = {3, 6, 8, 0, -1, 1, 4, 2}; 
+    std::vector<int> v = {3, 6, 8, -1, 7, 0, 9, 2, -11, 5};
     for(auto i : v){
         if(t.insert(i)) std::cout << "added " << i << "\n";
-        else std::cout << "failed at " << i << "\n";
+        else std::cout << "failed at adding " << i << "\n";
+        t.print();
+    }
+    for(auto i : v){
+        if(t.del(i)) std::cout << "deleted " << i << "\n";
+        else std::cout << "failed at deleting " << i << "\n";
         t.print();
     }
-    
-
 }