Merge pull request gzc426#320 from u-hechongyang/master

gzc426 · web-flow · commit f7c9fda09166 · 2018-12-05T13:04:27.000+08:00
3
diff --git a/2018.12.04-leetcode101/阳.md b/2018.12.04-leetcode101/阳.md
@@ -0,0 +1,32 @@
+/**
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ *     int val;
+ *     TreeNode left;
+ *     TreeNode right;
+ *     TreeNode(int x) { val = x; }
+ * }
+ */
+class Solution {
+	public boolean isSymmetric(TreeNode root) {
+		if(root == null) {
+			return true;//根节点为空，返回true
+		}else {
+			return isSymmetric(root.left, root.right);
+		}
+	}
+	public boolean isSymmetric(TreeNode pleft, TreeNode pright) {
+		if(pleft == null && pright == null) {
+			return true;//说明只有一个根节点，返回true
+		}
+		if(pleft == null || pright == null) {
+			return false;//一个子树为空，另一个子树不为空，返回false
+		}
+		//都不为空的情况下判断是否相等
+		if(pleft.val != pright.val) {
+			return false;
+		}
+		//继续判断左子树与右子树是否对称相等
+		return isSymmetric(pleft.left, pright.right)&&isSymmetric(pleft.right, pright.left);
+	}
+}
