[LeetCode-129] Sum Root to Leaf Numbers

Sum Root to Leaf Numbers

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.

 

历遍而已呀，累加一下val就好~

 

/**
 * Definition for binary tree
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
 * };
 */
class Solution {
public:
    int sumNumbers(TreeNode *root) {
        // Start typing your C/C++ solution below
        // DO NOT write int main() function
        if (NULL == root) {
            return 0;
        }
        stack<TreeNode*> node_stack;
        TreeNode *pf = NULL, *psl = NULL, *psr = NULL;
        node_stack.push(root);
        int sum = 0;
        while (!node_stack.empty()) {
            TreeNode* pf = node_stack.top();
            node_stack.pop();
            if ((NULL == pf->left) && (NULL == pf->right)) {
                sum += pf->val;
            } else {
                if (NULL != (psl = pf->left)) {
                    psl->val += pf->val * 10;
                    node_stack.push(psl);
                }
                if (NULL != (psr = pf->right)) {
                    psr->val += pf->val * 10;
                    node_stack.push(psr);
                }
            }
        }
        return sum;
    }
};