LeetCode——Sum Root to Leaf Numbers

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探讨了如何计算给定二叉树中从根节点到叶子节点的所有路径所表示的数字之和。

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.

» Solve this problem

/**
 * 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 ans;
    
    void sum(TreeNode *root, int cur) {
        if (!root) {
            return;
        }
        if (root->left || root->right) {
            sum(root->left, cur * 10 + root->val);
            sum(root->right, cur * 10 + root->val);            
        }
        else {
            ans += cur * 10 + root->val;
        }
    }
    
    int sumNumbers(TreeNode *root) {
        // Start typing your C/C++ solution below
        // DO NOT write int main() function
        ans = 0;
        sum(root, 0);
        return ans;
    }
};