113. Path Sum II-优快云博客

本文介绍了一种算法，用于在给定的二叉树中寻找所有从根节点到叶子节点的路径，这些路径上的节点值之和等于指定的目标值。通过递归方式遍历树结构，并实时更新路径值总和。

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Given a binary tree and a sum, find all root-to-leaf paths where each path's sum equals the given sum.

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

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

return

[
   [5,4,11,2],
   [5,8,4,5]
]

/**
 * 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 {
private:
    vector<vector<int>> result;
public:
    
    void pathPlus(TreeNode * root, int sum, vector<int> &vec)
    {
        if(root->left==NULL && root->right==NULL)
        {
            vector<int>::iterator iter = vec.begin();
            int totalsum = 0;
            for( ; iter != vec.end() ; iter++)
            {
                totalsum += *iter;
            }
            
            if(totalsum == (sum-root->val))
            {
                vec.push_back(root->val);
                result.push_back(vec);
                vec.pop_back();
            }   
            return;
        }
        
        cout<<root->val<<endl;
        
        vec.push_back(root->val);
        if(root->left)
            pathPlus(root->left, sum, vec);
        if(root->right)    
            pathPlus(root->right, sum, vec);
        vec.pop_back();
    }
    
    void pathMinus(TreeNode * root, int sum, vector<int> &vec)
    {
        if(root->left==NULL && root->right==NULL && sum == root->val)
        {
                       
                vec.push_back(root->val);
                result.push_back(vec);
                vec.pop_back();
                return;
        }
        
        cout<<root->val<<endl;
        
        vec.push_back(root->val);
        if(root->left)
            pathMinus(root->left, sum-root->val, vec);
        if(root->right)    
            pathMinus(root->right, sum-root->val, vec);
        vec.pop_back();
    }
    
    vector<vector<int>> pathSum(TreeNode* root, int sum) {
        
        if (root == NULL)
            return vector<vector<int>>();
        
        vector<int> vec;
        pathPlus(root, sum, vec);
        
        return result;
    }
};