You are given a binary tree in which each node contains an integer value.
Find the number of paths that sum to a given value.
The path does not need to start or end at the root or a leaf, but it must go downwards (traveling only from parent nodes to child nodes).
The tree has no more than 1,000 nodes and the values are in the range -1,000,000 to 1,000,000.
Example:
root = [10,5,-3,3,2,null,11,3,-2,null,1], sum = 8
10 / \ 5 -3 / \ \ 3 2 11 / \ \ 3 -2 1
Return 3. The paths that sum to 8 are:
1. 5 -> 3 2. 5 -> 2 -> 1 3. -3 -> 11
来源:力扣(LeetCode) 链接:https://leetcode-cn.com/problems/path-sum-iii
/**
* 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<int>sums;
int count=0;
void travel(TreeNode * root ,int level ,int sum){
if(root==NULL){return ;}
sums[level] = sums[level-1]+root->val;
for(int i=0;i<level;i++){
if(sums[level]-sums[i]==sum)count++;
}
travel(root->left,level+1,sum);
travel(root->right,level+1,sum);
}
int pathSum(TreeNode* root, int sum) {
if(root == NULL){return 0;}
sums.resize(maxDepth(root)+1,0);
travel(root,1,sum);
return count;
}
int maxDepth(TreeNode * root){
if(root==NULL)return 0;
return max(maxDepth(root->left),maxDepth(root->right))+1;
}
};