[not completed]leetcode contest biweekly 17

OneCodeMonkey · OneCodeMonkey · commit 60367aeb6e65 · 2020-01-11T23:22:03.000+08:00
diff --git a/contest/leetcode_biweek_17_problems/leetcode_5145_Sum_of_Nodes_with_Even-Valued_Grandparent.cpp b/contest/leetcode_biweek_17_problems/leetcode_5145_Sum_of_Nodes_with_Even-Valued_Grandparent.cpp
@@ -1,3 +1,9 @@
+/**
+ * AC:
+ * 思路：递归，定义 f(node), 对于每一个 node，判断到孙子节点，如果当前 node->val 为偶，
+ *    则加进其孙子节点的值（如果存在）,然后 再递归累加 ret += f(node->left) + f(node->right)
+ * T:O(n), n 为二叉树的节点数
+ */
 /**
  * Definition for a binary tree node.
  * struct TreeNode {
@@ -10,6 +16,32 @@
 class Solution {
 public:
     int sumEvenGrandparent(TreeNode* root) {
-        
+        TreeNode* tmp = root;
+        int ret = 0;
+        if(root->val % 2 == 0) {	// 偶数点
+        	if(root->left) {
+        		if(root->left->left)
+        			ret += root->left->left->val;
+        		if(root->left->right)
+        			ret += root->left->right->val;
+        		ret += sumEvenGrandparent(root->left);		// 递归
+        	}
+        	if(root->right) {
+        		if(root->right->left)
+        			ret += root->right->left->val;
+        		if(root->right->right)
+        			ret += root->right->right->val;
+        		ret += sumEvenGrandparent(root->right);
+        	}
+        } else {
+        	if(root->left) {
+        		ret += sumEvenGrandparent(root->left);		// 递归
+        	}
+        	if(root->right) {
+        		ret += sumEvenGrandparent(root->right);
+        	}
+        }
+
+        return ret;
     }
 };
