LeetCode 112. 路径总和

深度优先遍历

/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
 *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
 *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
 * };
 */
class Solution {
public:
    bool dfs(TreeNode* root, int targetSum)
    {
        if(!root)
            return false;

        targetSum -= root->val;

        if(!root->left && !root->right && targetSum == 0)
            return true;
        
        return dfs(root->left, targetSum) || dfs(root->right, targetSum);
    }
    bool hasPathSum(TreeNode* root, int targetSum) {
        return dfs(root, targetSum);
    }
};

广度优先遍历

/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
 *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
 *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
 * };
 */
class Solution {
public:
    bool hasPathSum(TreeNode* root, int targetSum) {
        if(!root)
        {
            return false;
        }

        queue<TreeNode*> que_node;
        queue<int> que_sum;
        que_node.push(root);
        que_sum.push(root->val);

        while(!que_node.empty())
        {
            int sum = que_sum.front();
            TreeNode* node = que_node.front();
            que_sum.pop();
            que_node.pop();

            if(!node->left && !node->right && sum == targetSum)
                return true;
            
            if(node->left)
            {
                que_node.push(node->left);
                que_sum.push(sum + node->left->val);
            }
            if(node->right)
            {
                que_node.push(node->right);
                que_sum.push(sum + node->right->val);
            }
        }
        return false;
    }
};