leetcode Sum Root to Leaf Numbers
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题意较为清晰易懂,即遍历二叉树中所有从根到叶子的结点的值并求和。
可以使用DFS来实现算法。
但是难点在于如何保存中间结果。
参考网上的结论,可以在遍历过程中改变结点的val数值,该数值即为从根节点到当前节点的数,因此每到一个叶子节累加该叶子节点的val值,最后的累加结果即为所求。
代码
class Solution{public:int sumNumbers(TreeNode *root){sumAll = 0; dfsSum(root);return sumAll;}void dfsSum(TreeNode *root){TreeNode *p;if(p==NULL)return ;if(p->left==NULL&&p->right==NULL){sumAll += p->val;return;}if(p->left!=NULL){p->left->val += p->val*10;dfsSum(p->left);}if(p->right!=NULL){p->right->val += p->val*10;dfsSum(p->right);}}private:int sumAll;};
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