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Path Sum II.cpp
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Path Sum II.cpp
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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 binary tree
* struct TreeNode {
* int val;
* TreeNode *left;
* TreeNode *right;
* TreeNode(int x) : val(x), left(NULL), right(NULL) {}
* };
*/
class Solution {
public:
vector<vector<int> > pathSum(TreeNode *root, int sum) {
// IMPORTANT: Please reset any member data you declared, as
// the same Solution instance will be reused for each test case.
vector<vector<int> > ret;
if (root == nullptr) {
return ret;
}
do_pathsum(root, sum, ret);
return ret;
}
void do_pathsum(TreeNode *root, const int sum, vector<vector<int> > &ret) {
static int cur = 0;
static vector<int> s;
cur += root->val; // update current sum
s.push_back(root->val);
if (root->left != nullptr)
do_pathsum(root->left, sum, ret);
if (root->right != nullptr)
do_pathsum(root->right, sum, ret);
if (root->left == nullptr && root->right == nullptr) { // base case
if (sum == cur) {
ret.push_back(s);
}
}
s.pop_back(); // backtracking
cur -= root->val;
}
};