Given a binary tree and a sum, determine if the tree has a root-to-leaf path such that adding up all the values along the path equals the given sum.
For example:Given the below binary tree and
sum = 22
,
5
/ \
4 8
/ / \
11 13 4
/ \ \
7 2 1
return true, as there exist a root-to-leaf path 5->4->11->2 which sum is 22.
这个题目用递归做很简单，分类讨论即可。
class Solution {
public:
bool hasPathSum(TreeNode *root, int sum) {
if( root == NULL ) return false;
if( root -> left == NULL && root -> right == NULL ) {
if( root -> val == sum ) return true;
else return false;
}
else if( root -> left == NULL )
return hasPathSum( root -> right,sum - root -> val );
else if( root -> right == NULL )
return hasPathSum( root -> left,sum - root -> val );
else
return hasPathSum( root -> left,sum - root -> val ) || hasPathSum( root -> right,sum - root -> val );
}
};