Pathsum
Description:
Given a binary tree and a sum, determine if the tree has a root-to-leaf path such that adding up all the values along the path equals the given sum.
For example:
Given the below binary tree and sum
=22,
5
/ 4 8
/ / 11 13 4
/ \ 7 2 1
return true, as there exist a root-to-leaf
path 5->4->11->2 which sum is 22.
分析：二叉树root-to-leaf的查找，深搜搜到结果返回即可
1 /** 2 * Definition for binary tree 3 * struct TreeNode { 4 * int val; 5 * TreeNode *left; 6 * TreeNode *right; 7 * TreeNode(int x) : val(x), left(NULL), right(NULL) {} 8 * }; 9 */ 10 class Solution { 11 public: 12 bool hasPathSum(TreeNode *root, int sum) { 13 if(root==NULL) return false; 14 int sumval = root->val; 15 if(sumval==sum && root->left==NULL &&root->right==NULL) return true; 16 else{ 17 return (hasPathSum(root->left,sum-sumval)||hasPathSum(root->right,sum-sumval)); 18 } 19 } 20 };
PathsumII
Description:
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] ]
分析：这一题和上一题的区别在于不仅需要判断有没有，还需要记录是什么。在深搜的时候维护一个stack（这里用vector实现），记录已经走过的路径，
返回是栈也弹出相应节点
1 /** 2 * Definition for binary tree 3 * struct TreeNode { 4 * int val; 5 * TreeNode *left; 6 * TreeNode *right; 7 * TreeNode(int x) : val(x), left(NULL), right(NULL) {} 8 * }; 9 */ 10 class Solution { 11 public: 12 bool pathrec(vector<vector<int> > &rec, vector<int>& path,TreeNode* r,int sum) 13 { 14 sum-=r->val; 15 //if(sum<0) return false; 16 //Tell if it‘s a leaf node 17 if(r->left ==NULL && r->right == NULL) 18 { 19 if(sum!=0) return false; 20 else{ 21 vector<int> one = path; 22 one.push_back(r->val); 23 rec.push_back(one); 24 return true; 25 } 26 } 27 //Ordinary node 28 path.push_back(r->val); 29 bool flag = false; 30 if(r->left!=NULL) pathrec(rec,path,r->left,sum); 31 if(r->right!=NULL) pathrec(rec,path,r->right,sum); 32 path.erase(path.end()-1); 33 return flag; 34 35 } 36 vector<vector<int> > pathSum(TreeNode *root, int sum) { 37 vector<vector<int> > rec; 38 if(root==NULL) return rec; 39 vector<int> path; 40 pathrec(rec,path,root,sum); 41 42 return rec; 43 } 44 };
Leetcode::Pathsum & Pathsum II,布布扣,bubuko.com
Leetcode::Pathsum & Pathsum II
原文：http://www.cnblogs.com/soyscut/p/3774526.html