Merge pull request gzc426#285 from gityjx/master

gzc426 · web-flow · commit fbdab49a18e8 · 2018-12-03T19:47:09.000+08:00
upload
diff --git a/2018.12.4-leetcode101/halfofwater.md b/2018.12.4-leetcode101/halfofwater.md
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+## Leetcode 101
+
+
+### 递归解法:
+
+``` C++
+/**
+ * Definition for a binary tree node.
+ * struct TreeNode {
+ *     int val;
+ *     TreeNode *left;
+ *     TreeNode *right;
+ *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
+ * };
+ */
+class Solution {
+public:
+    bool isSymmetric(TreeNode* root) {
+        return helper(root, root);
+    }
+    bool helper(TreeNode *left, TreeNode *right) {
+	if (left == NULL && right == NULL) return true;
+	if (left == NULL || right == NULL) return false;
+
+	if (left->val != right->val) return false;
+	return helper(left->left, right->right) && helper(left->right, right->left);
+
+}
+};
+
+``` 
+
+### 迭代解法:
+``` C++
+/**
+ * Definition for a binary tree node.
+ * struct TreeNode {
+ *     int val;
+ *     TreeNode *left;
+ *     TreeNode *right;
+ *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
+ * };
+ */
+class Solution {
+public:
+    bool isSymmetric(TreeNode* root) {
+        	std::queue<TreeNode *> q;
+	q.push(root);
+	q.push(root);
+	while (!q.empty()) {
+		TreeNode* t1 = q.front();
+        q.pop();
+		TreeNode* t2 = q.front();
+		q.pop();
+		if (t1 == NULL && t2 == NULL)	continue;
+		if (t1 == NULL || t2 == NULL)	return false;
+		if (t1->val != t2->val)	return false;
+		q.push(t1->left);
+		q.push(t2->right);
+		q.push(t1->right);
+		q.push(t2->left);
+	}
+	return true;
+    }
+};
+
+```
