LeetCode404.左叶子之和

题目

法一、广度优先搜索

 1 class Solution {
 2 public:
 3     int sumOfLeftLeaves(TreeNode* root) {
 4         if(root == NULL) return 0;
 5         if(root->left == NULL && root->right == NULL) return 0;
 6         int sum = 0;
 7         queue<TreeNode*>que;
 8         que.push(root);
 9         while(!que.empty()){
10             TreeNode* node = que.front();que.pop();
11             if(node->left != NULL) {
12                 que.push(node->left);
13                 if(node->left->left == NULL && node->left->right == NULL)
14                     sum += node->left->val;
15             }
16             if(node->right != NULL) {
17                 que.push(node->right);
18             }
19         }
20         return sum;
21     }
22 };

法二、深搜

 1 class Solution {
 2 public:
 3      bool isLeafNode(TreeNode *root){
 4         return (!root->left && !root->right);
 5      }
 6
 7      int dfs(TreeNode* root){
 8         int sum = 0;
 9         if(root->left != NULL){
10             if(root->left != NULL && isLeafNode(root->left))
11                 sum += root->left->val;
12             if(!isLeafNode(root->left))
13                 sum += dfs(root->left);
14         }
15         if(root->right != NULL && !isLeafNode(root->right))
16             sum += dfs(root->right);
17         return sum;
18     }
19
20     int sumOfLeftLeaves(TreeNode* root) {
21         if(root == NULL) return 0;
22         return dfs(root);
23     }
24
25
26 };