题解 | #二叉树根节点到叶子节点的所有路径和#

这道题不难直接dfs爆搜 但是有坑点 需要两次回溯 找到叶子节点的时候和一个节点搜完都要回溯一下

 * struct TreeNode {
 *	int val;
 *	struct TreeNode *left;
 *	struct TreeNode *right;
 * };
 */

class Solution {
public:
    /**
     * 
     * @param root TreeNode类 
     * @return int整型
     */
    vector<int> v;
    int ans = 0;
    
    int sumcnt(vector<int> mv){
        int sum = 0;
        for(int i=0;i<mv.size();i++){
            sum = 10*sum + mv[i];
        }
        return sum;
    }
    
    
    
    void dfs(TreeNode* root){
        if(root->left == NULL && root->right == NULL){
            v.push_back(root->val);
            ans += sumcnt(v);
            v.pop_back();//回溯
            return ;
        }
        v.push_back(root->val);
       if(root->left != NULL) dfs(root->left);
       if(root->right != NULL) dfs(root->right);
        v.pop_back();//回溯
    }
    
    
    
    
    int sumNumbers(TreeNode* root) {
        if(root == NULL) return 0;
        dfs(root);
        return ans;
    }
};