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题目要求：
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.
这道题采用深度优先搜索的方法就可以了，具体程序（12ms）如下：
1 /** 2 * Definition for a binary tree node. 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) 14 return false; 15 return hasPathSumSub(root, 0, sum); 16 } 17 18 bool hasPathSumSub(TreeNode *tree, int subSum, int sum) 19 { 20 if(!tree) 21 return false; 22 23 subSum += tree->val; 24 if(!tree->left && !tree->right && subSum == sum) 25 return true; 26 27 return hasPathSumSub(tree->left, subSum, sum) || hasPathSumSub(tree->right, subSum, sum); 28 } 29 };
题目要求：
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] ]
这题与上题类似。具体程序（24ms）如下：
1 /** 2 * Definition for a binary tree node. 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 vector<vector<int>> pathSum(TreeNode* root, int sum) { 13 vector<vector<int>> rVec; 14 if(!root) 15 return rVec; 16 17 vector<int> vec; 18 hasPathSumSub(root, vec, rVec, 0, sum); 19 return rVec; 20 } 21 22 void hasPathSumSub(TreeNode *tree, vector<int> vec, vector<vector<int>>& rVec, int subSum, int sum) 23 { 24 if(!tree) 25 return; 26 27 vec.push_back(tree->val); 28 subSum += tree->val; 29 if(!tree->left && !tree->right && subSum == sum) 30 rVec.push_back(vec); 31 32 hasPathSumSub(tree->left, vec, rVec, subSum, sum); 33 hasPathSumSub(tree->right, vec, rVec, subSum, sum); 34 } 35 };
LeetCode之“树”：Path Sum && Path Sum II
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原文地址：http://www.cnblogs.com/xiehongfeng100/p/4629988.html
