【LeetCode】112. Path Sum

Given a binary tree and a sum, determine if the tree has a root-to-leaf path such that adding up all the values along the path equals the given sum.

For example:
Given the below binary tree and sum = 22,

              5
             / \
            4   8
           /   / \
          11  13  4
         /  \      \
        7    2      1

return true, as there exist a root-to-leaf path 5->4->11->2 which sum is 22.

 

Solution 1

class Solution {
public:
    bool hasPathSum(TreeNode* root, int sum) {
        if (!root)
            return false;
        if (!root->left && !root->right && root->val == sum)
            return true;
        return hasPathSum(root->left, sum - root->val)
                || hasPathSum(root->right, sum - root->val);
    }
};

 

Solution 2

class Solution {
public:
    bool hasPathSum(TreeNode* root, int sum) {
        if (!root)
            return false;
        queue<TreeNode*> que;
        que.push(root);
        queue<int> qsum;
        qsum.push(root->val);
        
        while (!que.empty()) {
            TreeNode* cur = que.front();
            que.pop();
            int num = qsum.front();
            qsum.pop();
            
            if (!cur->left && !cur->right && num == sum) {
                return true;
            }
            if (cur->left) {
                que.push(cur->left);
                qsum.push(cur->left->val + num);
            }
            if (cur->right) {
                que.push(cur->right);
                qsum.push(cur->right->val + num);
            }
        }
        return false;
    }
};