LeetCode 113. Path Sum II 动态演示

给第一个目标值，返回一棵树从根到叶子所有和等于目标值的路径。

经典的深度优先算法

/**
 * 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:
    void helper(TreeNode* cur, int sum, int target, vector<int>& output, vector<vector<int>>& ret){
        //a(cur)
        //lk("root",cur)
        //a(sum)
        //a(target)
        //dsp
        if(!cur->left && !cur->right){
            if(sum==target){
                ret.push_back(output);                
            }
            return;
        }
        
        if(cur->left){
            output.push_back(cur->left->val);
            helper(cur->left, sum+cur->left->val, target, output, ret);
            output.pop_back();    
        }
        
        if(cur->right){
            output.push_back(cur->right->val);
            helper(cur->right, sum+cur->right->val, target, output, ret);
            output.pop_back();    
        }        
    }
    
    vector<vector<int>> pathSum(TreeNode* root, int sum) {        
        vector<int> output;
        vector<vector<int>> ret;
        //ahd(root)
        //a(ret)
        //a(output)
        if(!root)
            return ret;
        
        output.push_back(root->val);
        helper(root, root->val, sum, output, ret);
        return ret;    
    }
};

程序运行动态演示 http://simpledsp.com/FS/Html/lc113.html