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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.
判断是否存在从根节点到叶子节点的值相加结果为给定的值,存在返回true,否则false;
//深度优先 维护要完成的剩余目标值
public boolean hasPathSum(TreeNode root, int sum) {
if(root ==null){//以最后空接点作为递归结束
return false;
}
//满足题意的结束条件
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) ;
}