小白笔记----------------leetcode(404. Sum of Left Leaves )

主要考虑如何判断是否是该树的左子叶，先从根节点开始，然后分别从左右子树开始递归，最终求得最后的总和

/** * Definition for a binary tree node. * struct TreeNode { *     int val; *     struct TreeNode *left; *     struct TreeNode *right; * }; */int sumOfLeftLeaves(struct TreeNode* root) {      if(root == NULL) return 0;      if(root->left != NULL){          if(root->left->left == NULL && root->left->right == NULL){              return root->left->val + sumOfLeftLeaves(root->right);          }      }      return sumOfLeftLeaves(root->left) + sumOfLeftLeaves(root->right);}