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.
//深度優先 維護要完成的剩餘目標值
public boolean hasPathSum(TreeNode root, int sum) {
if(root ==null){//以最後空接點作爲遞歸結束
return false;
}
//滿足題意的結束條件
if(root.left ==null && root.right ==null && root.val == sum){
return true;
}
return hasPathSum(root.left, sum - root.val) || hasPathSum(root.right, sum - root.val) ;
}