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SumRoottoLeafNumbers.h
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93 lines (80 loc) · 2.09 KB
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/*
Given a binary tree containing digits from 0-9 only, each root-to-leaf path could represent a number.
An example is the root-to-leaf path 1->2->3 which represents the number 123.
Find the total sum of all root-to-leaf numbers.
For example,
1
/ \
2 3
The root-to-leaf path 1->2 represents the number 12.
The root-to-leaf path 1->3 represents the number 13.
Return the sum = 12 + 13 = 25.*/
/**
* Definition for a binary tree node.
* struct TreeNode {
* int val;
* TreeNode *left;
* TreeNode *right;
* TreeNode(int x) : val(x), left(NULL), right(NULL) {}
* };
*/
class Solution {
public:
int sumNumbers(TreeNode* root) {
stack<TreeNode*> nodes;
if (!root)
return 0;
int total = 0;
int current = 0;
TreeNode* last = nullptr;
while (root || !nodes.empty())
{
if (root)
{
nodes.push(root);
current *= 10;
current += root->val;
root = root->left;
}
else
{
root = nodes.top();
if (root->right && root->right != last)
{
root = root->right;
}
else
{
nodes.pop();
last = root;
// only add sum of leaf node
if (root->right == NULL && root->left == NULL)
total += current;
current /= 10;
root = NULL;
}
}
}
return total;
}
};
/*class Solution {
public:
int sumNumbers(TreeNode* root) {
total = 0;
helper(root, 0);
return total;
}
private:
void helper(TreeNode*root, int sum) {
if (root == NULL) return;
sum = sum * 10 + root->val;
if (root->left == NULL && root->right == NULL) {
total += sum;
return;
}
helper(root->left, sum);
helper(root->right, sum);
}
int total;
};*/