题目:给定一颗二叉树以及一个sum,判断在二叉树中是否存在一条路径,使得路径上节点值之和等于sum
算法:深度优先搜索
/**
* Definition for binary tree
* public class TreeNode {
* int val;
* TreeNode left;
* TreeNode right;
* TreeNode(int x) { val = x; }
* }
*/
public class Solution {
public boolean hasPathSum(TreeNode root, int sum) {
if (root == null) {
return false;
}
return dfs(root, root.val, sum);
}
public boolean dfs(TreeNode node, int sum, int target) {
if (node.left==null && node.right==null && sum==target) {
return true;
}
if (node.left != null) {
if (dfs(node.left, sum+node.left.val, target)) {
return true;
}
}
if (node.right != null) {
if (dfs(node.right, sum+node.right.val, target)) {
return true;
}
}
return false;
}
}