222. 完全二叉树的节点个数

src/com/gatsby/_222CountCompleteTreeNodes.java

@@ -0,0 +1,58 @@
+package com.gatsby;
+
+import java.util.Objects;
+
+/**
+ * @ClassName: _222CountCompleteTreeNodes
+ * @Description: leetcode 222 完全二叉树的节点数量
+ * @author: Gatsby
+ * @date: 2022/7/29 10:48
+ */
+
+public class _222CountCompleteTreeNodes {
+    /**
+     * @MethodName: countNodes
+     * @Parameter: [root]
+     * @Return int
+     * @Description: 递归
+     * @author: Gatsby
+     * @date: 2022/7/29 10:50
+     */
+    public int countNodes(TreeNode root) {
+        if (Objects.isNull(root)) {
+            return 0;
+        } else return countNodes(root.left) + countNodes(root.right) + 1;
+    }
+
+    /**
+     * @MethodName: countNodesBs
+     * @Parameter: [root]
+     * @Return int
+     * @Description: 二分查找
+     * @author: Gatsby
+     * @date: 2022/7/29 10:58
+     */
+    public int countNodesBs(TreeNode root) {
+        if (Objects.isNull(root)) return 0;
+        int left = countHeight(root.left);
+        int right = countHeight(root.right);
+
+        // 如果左子树和右子树的深度相等，那么左子树一定是个满二叉树，加上一个root节点
+        // 直接用1 << left计算就行
+        if (left == right) {
+            return countNodesBs(root.right) + (1 << left);
+        }
+        return countNodesBs(root.left) + (1 << right);
+    }
+
+    private int countHeight(TreeNode root) {
+        int height = 0;
+        while (!Objects.isNull(root)) {
+            height++;
+            root = root.left;
+        }
+        return height;
+    }
+}
+
+