437. Path Sum III

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.

- 列表内容

/**
* Definition for a binary tree node.
* struct TreeNode {
*     int val;
*     struct TreeNode *left;
*     struct TreeNode *right;
* };
*/
int pathSumRoot(struct TreeNode* root,int sum) {
int count = 0;
if(root == NULL){
return count;
}

if(root->val == sum){
count++;
}

/*left node*/
if(root->left){
count += pathSumRoot(root->left,sum-root->val);
}

/*right node*/
if(root->right){
count += pathSumRoot(root->right,sum-root->val);
}

return count;
}

int pathSum(struct TreeNode* root, int sum) {
int count = 0;

if(root == NULL){
return 0;
}

if(root->left == NULL && root->right == NULL){
if(root->val == sum){
return 1;
}else{
return 0;
}
}

return pathSumRoot(root,sum) + pathSum(root->left,sum) + pathSum(root->right,sum);
}