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DFS

  1. public class Solution {
  2.     public boolean hasPathSum(TreeNode root, int sum) {
  3.         if(root == null){
  4.             return false;
  5.         }
  6.         if(root.left == null && root.right == null){
  7.             return root.val == sum;
  8.         }
  9.         return hasPathSum(root.left, sum - root.val) || hasPathSum(root.right, sum - root.val);
  11.     }
  12. }