二分搜索树

Author: tianqing.liang

10-Binary-Search-Tree/BST.dart

@@ -0,0 +1,192 @@
+/**
+ * 二分搜索树
+ */
+class BST<T extends Comparable<T>> {
+  _Node? root;
+
+  int? size;
+
+  BST() {
+    root = null;
+    size = 0;
+  }
+
+  int? getSize() {
+    return size;
+  }
+
+  bool isEmpty() {
+    return size == 0;
+  }
+
+  //添加元素
+//  add(T t) {
+//    if (root == null) {
+//      root = _Node(t);
+//      size = size! + 1;
+//    } else {
+//      addNext(root, t);
+//    }
+//  }
+  add(T e) {
+    root = addNext(root, e);
+  }
+
+//  向以node为根的二分搜索树中插入元素e，递归算法
+//  addNext(_Node? node, T? t) {
+//    if (t! == node!.e)
+//      return;
+//    else if (t.compareTo(node.e) < 0 && node.left == null) {
+//      node.left = _Node(t);
+//      size = size! +1;
+//      return;
+//    } else if (t.compareTo(node.e) > 0 && node.right == null) {
+//      node.right = _Node(t);
+//      size = size! +1;
+//      return;
+//    }
+//    if (t.compareTo(node.e) < 0)
+//      addNext(node.left, t);
+//    else //e.compareTo(node.e) > 0
+//      addNext(node.right, t);
+//  }
+  //返回新节点后二分搜索树的根
+  _Node addNext(_Node? node, T t) {
+    if (node == null) {
+      size = size! + 1;
+      return _Node(t);
+    }
+    if (t.compareTo(node.e) < 0) {
+      node.left = addNext(node.left, t);
+    } else if (t.compareTo(node.e) > 0) {
+      node.right = addNext(node.right, t);
+    }
+    return node;
+  }
+
+  // 向二分搜索树中添加新的元素e，非递归写法
+  add2(T e) {
+    if (root == null) {
+      root = _Node(e);
+      size = size! + 1;
+      return;
+    }
+    _Node? p = root;
+    while (p != null) {
+      if (e.compareTo(p.e) < 0) {
+        if (p.left == null) {
+          p.left = _Node(e);
+          size = size! + 1;
+          return;
+        }
+        p = p.left;
+      } else if (e.compareTo(p.e) > 0) {
+        if (p.right == null) {
+          p.right = _Node(e);
+          size = size! + 1;
+          return;
+        }
+        p = p.right;
+      } else
+        return;
+    }
+  }
+
+  //查询元素是否包含
+  bool contains(T t) {
+    return _containsAll(root, t);
+  }
+
+  bool _containsAll(_Node? node, T t) {
+    if (node == null) {
+      return false;
+    }
+    if (t.compareTo(node.e) == 0) {
+      return true;
+    } else if (t.compareTo(node.e) < 0) {
+      return _containsAll(node.left, t);
+    } else {
+      return _containsAll(node.right, t);
+    }
+  }
+
+  // 二分搜索树的前序遍历
+  preOrder() {
+    _preOrderDetail(root!);
+  }
+
+  _preOrderDetail(_Node? node) {
+    if (node == null) {
+      return;
+    }
+    print(node.e);
+    _preOrderDetail(node.left);
+    _preOrderDetail(node.right);
+  }
+
+  inOrder() {
+    _inOrderDetail(root);
+  }
+
+  _inOrderDetail(_Node? node) {
+    if (node == null) {
+      return;
+    }
+    _inOrderDetail(node.left);
+    print(node.e);
+    _inOrderDetail(node.right);
+  }
+
+  postOrder() {
+    _postOrderDetail(root);
+  }
+
+  _postOrderDetail(_Node? node) {
+    if (node == null) {
+      return;
+    }
+    _postOrderDetail(node.left);
+
+    _postOrderDetail(node.right);
+    print(node.e);
+  }
+
+  @override
+  String toString() {
+    StringBuffer res = new StringBuffer();
+    _generateBSTString(root!, 0, res);
+    return res.toString();
+  }
+
+  _generateBSTString(_Node? node, int depth, StringBuffer res) {
+    if (node == null) {
+      res.write("${_generateBSTStringDepth(depth)} null \n");
+      return;
+    }
+    res.write("${_generateBSTStringDepth(depth)} ${node.e} \n");
+    _generateBSTString(node.left, depth + 1, res);
+    _generateBSTString(node.right, depth + 1, res);
+  }
+
+  _generateBSTStringDepth(int depth) {
+    StringBuffer res = new StringBuffer();
+    for (int i = 0; i < depth; i++) {
+      res.write(" - -");
+    }
+    return res.toString();
+  }
+}
+
+class _Node<T> {
+  T? e;
+
+  _Node? left;
+
+  _Node? right;
+
+  _Node(T t) {
+    this.e = t;
+    this.left = null;
+    this.right = null;
+  }
+}

10-Binary-Search-Tree/Main.dart

@@ -0,0 +1,19 @@
+import 'BST.dart';
+void main(){
+  BST<num> bst = new BST<num>();
+  var list =[5,3,6,8,4,2];
+  for(var i = 0;i<list.length;i++){
+    bst.add(list[i]);
+  }
+  //前序遍历
+  bst.preOrder();
+  print(bst);
+
+  //中序遍历
+  bst.inOrder();
+  print(bst);
+
+  //后序遍历
+  bst.postOrder();
+  print(bst);
+}

README.md

@@ -11,6 +11,7 @@
 7. 归并排序,归并排序排序优化,自底向上排序
 8. 快速排序,快速排序优化，二路快排，三路快排
 9. 二分搜索,二分搜索优化
+10. 二分搜索树
 
 #### SDK版本
 1. 版本：2.12.3