437. Path Sum III
2017-11-16 09:44
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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:
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
1 class Solution { 2 3 public int pathSum(TreeNode root, int sum) { 4 if(root==null) return 0; 5 int res = path(root,sum)+pathSum(root.right,sum)+pathSum(root.left,sum); 6 return res; 7 8 } 9 10 private int path(TreeNode root, int sum) { 11 int res=0; 12 if(root==null) 13 return res ; 14 if(sum==root.val) 15 res+=1; 16 res+=path(root.left,sum-root.val); 17 res+=path(root.right,sum-root.val); 18 return res; 19 } 20 21 }
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