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package DepthFirstSearch;

import Tree.TreeNode;

/*

* 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.

* 在递归中如何在递归过程中从底层直接返回

*/

public class PathSum {

public boolean hasPathSum(TreeNode root, int sum) {

return dfsFunction(root, sum, 0);

}

private boolean dfsFunction(TreeNode node, int sum, int cursum){

if(node == null)

return false;

if(node.getLeft() == null && node.getRight() == null)

return node.getVal() + cursum == sum;

return dfsFunction(node.getLeft(), sum, cursum + node.getVal()) || (dfsFunction(node.getRight(), sum, cursum + node.getVal()));

}

}