Create BinarySearchTree.java

java/24_tree/BinarySearchTree.java

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+public class BinarySearchTree {
+  private Node tree;
+
+  public Node find(int data) {
+    Node p = tree;
+    while (p != null) {
+      if (data < p.data) p = p.left;
+      else if (data > p.data) p = p.right;
+      else return p;
+    }
+    return null;
+  }
+
+  public void insert(int data) {
+    if (tree == null) {
+      tree = new Node(data);
+      return;
+    }
+
+    Node p = tree;
+    while (p != null) {
+      if (data > p.data) {
+        if (p.right == null) {
+          p.right = new Node(data);
+          return;
+        }
+        p = p.right;
+      } else { // data < p.data
+        if (p.left == null) {
+          p.left = new Node(data);
+          return;
+        }
+        p = p.left;
+      }
+    }
+  }
+
+  public void delete(int data) {
+    Node p = tree; // p指向要删除的节点，初始化指向根节点
+    Node pp = null; // pp记录的是p的父节点
+    while (p != null && p.data != data) {
+      pp = p;
+      if (data > p.data) p = p.right;
+      else p = p.left;
+    }
+    if (p == null) return; // 没有找到
+
+    // 要删除的节点有两个子节点
+    if (p.left != null && p.right != null) { // 查找右子树中最小节点
+      Node minP = p.right;
+      Node minPP = p; // minPP表示minP的父节点
+      while (minP.left != null) {
+        minPP = minP;
+        minP = minP.left;
+      }
+      p.data = minP.data; // 将minP的数据替换到p中
+      p = minP; // 下面就变成了删除minP了
+      pp = minPP;
+    }
+
+    // 删除节点是叶子节点或者仅有一个子节点
+    Node child; // p的子节点
+    if (p.left != null) child = p.left;
+    else if (p.right != null) child = p.right;
+    else child = null;
+
+    if (pp == null) tree = child; // 删除的是根节点
+    else if (pp.left == p) pp.left = child;
+    else pp.right = child;
+  }
+
+  public static class Node {
+    private int data;
+    private Node left;
+    private Node right;
+
+    public Node(int data) {
+      this.data = data;
+    }
+  }
+}