acwing 47. 二叉树中和为某一值的路径

Posted 2022-08-23 itdef

地址 https://www.acwing.com/problem/content/description/45/

输入一棵二叉树和一个整数，打印出二叉树中结点值的和为输入整数的所有路径。

从树的根结点开始往下一直到叶结点所经过的结点形成一条路径。

给出二叉树如下所示，并给出num=22。
      5
     /     4   6
   /   /   12  13  6
 /  \    / 9    1  5   1

输出：[[5,4,12,1],[5,6,6,5]]

 

树的处理 一半是递归

/**
 * Definition for a binary tree node.
 * struct TreeNode 
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode(int x) : val(x), left(NULL), right(NULL) 
 * ;
 */
class Solution 
public:
   vector<vector<int>> ret;

void findPathInner(TreeNode* root, int sum, vector<int> v)

    sum -= root->val;
    v.push_back(root->val);

    if (sum == 0 && root->left == NULL && root->right == NULL) 
        ret.push_back(v);
        return;
    

    if(sum <0 ) return;


    if (root->left != NULL) 
        findPathInner(root->left, sum, v);
    
    if (root->right != NULL) 
        findPathInner(root->right, sum, v);
    




vector<vector<int>> findPath(TreeNode* root, int sum) 
    if (root == NULL) return ret;
    if (sum == 0) return ret;

    vector<int> v;
    sum -= root->val;
    v.push_back(root->val);
    if (sum < 0) return ret;
    if (sum == 0) 
        ret.push_back(v);
        return ret;
    
    if (root->left != NULL) 
        findPathInner(root->left, sum, v);
    
    if (root->right != NULL) 
        findPathInner(root->right, sum, v);
    

    return ret;



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