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Problem Path Sum

Problem Description: 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.

Solution: 递归

 1  public boolean hasPathSum(TreeNode root, int sum) { 2        if (root == null) return false; 3         if (root.left == null  && root.right == null) return root.val == sum; 4         else { 5             if (root.left != null) {  6                 return hasPathSum(root.left, sum - root.val) ? true : hasPathSum(root.right, sum - root.val); 7             } else { 8                 return hasPathSum(root.right, sum - root.val); 9             }10 11         }12     }