Sum Root to Leaf Numbers (LeetCode)

Question:

https://oj.leetcode.com/problems/sum-root-to-leaf-numbers/

 

解答：

没什么好说的。碰到树遍历的问题要不DFS，要不BFS, BFS可以递归或者Iterative。

/**
 * Definition for binary tree
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
 * };
 */
class Solution {
    
    typedef pair<TreeNode*, int> TreePair;
public:
    int sumNumbers(TreeNode *root) {
        
        if (!root)
            return 0;
        
        std::queue<TreePair> q;
        q.push(TreePair(root, root->val));
        
        int sum = 0;
        
        while (!q.empty()) 
        {
            TreePair& p = q.front(); 
            TreeNode* leftChild = p.first->left;
            TreeNode* rightChild = p.first->right;
            
            if (!leftChild && !rightChild)
            {
                // found a leaf
                sum += p.second;
            }
            
            if (leftChild)
                q.push(TreePair(leftChild, p.second*10+leftChild->val));
                
            if (rightChild)
                q.push(TreePair(rightChild, p.second*10+rightChild->val));
            
            q.pop();
        }
        
        return sum;
    }
};