Given a binary tree and an integer K. Find the number of paths in the tree which have their sum equal to K.
A path may start from any node and end at any node in the downward direction.
Example 1:
Input:
Tree =
1
/ \
2 3
K = 3
Output: 2
Explanation:
Path 1 : 1 + 2 = 3
Path 2 : only leaf node 3
Example 2:
Input:
Tree =
1
/ \
3 -1
/ \ / \
2 1 4 5
/ / \ \
1 1 2 6
K = 5
Output: 8
Explanation:
The following paths sum to K.
3 2
3 1 1
1 3 1
4 1
1 -1 4 1
-1 4 2
5
1 -1 5
Your Task:
You don't need to read input or print anything. Complete the function sumK() which takes root node and integer K as input parameters and returns the number of paths that have sum K. Since the answer may be very large, compute it modulo 10^{9}+7.
Expected Time Complexity: O(N)
Expected Auxiliary Space: O(Height of Tree)
Constraints:
1 ≤ N ≤ 10^{5}
-10^{5} ≤ Node Value ≤ 10^{5}
-10^{9} ≤ k ≤ 10^{9}

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