Find the sum of all left leaves in a given binary tree.
Example:
3
/ 9 20
/ 15 7
There are two left leaves in the binary tree, with values 9 and 15 respectively. Return 24.
题目要求树的所有左叶节点的和，根据题意判断出所有左叶节点，使用递归即可。
class Solution { public: int sumOfLeftLeaves(TreeNode* root) { if (root == nullptr) return 0; if (root->left != nullptr && root->left->left == nullptr && root->left->right == nullptr) return root->left->val + sumOfLeftLeaves(root->right); return sumOfLeftLeaves(root->left) + sumOfLeftLeaves(root->right); } }; // 6 ms
原文：http://www.cnblogs.com/immjc/p/7185703.html