LeetCode 112—路径总和

递归：

 public boolean hasPathSum(TreeNode root, int sum) {
		 if(root==null) return false;
		 if(root.left==null&&root.right==null&&sum==0) return true;
		 return hasPathSum(root.left, sum-root.val)||hasPathSum(root.right, sum-root.val);
	        
	    }

迭代：

public boolean hasPathSum(TreeNode root, int sum) {
		 if (root==null) return false;
	     Stack<TreeNode> stack=new Stack<TreeNode>();
	     stack.push(root);
	     while (!stack.empty()) {
	            TreeNode t = stack.pop();
	            if (t.left==null && t.right==null) {
	                if (t.val == sum) return true;
	            }
	            if (t.right!=null) {
	                t.right.val += t.val;
	                stack.push(t.right);
	            }
	            if (t.left!=null) {
	                t.left.val += t.val;
	                stack.push(t.left);
	            }
	        }
	        return false;

		 
		 
	 }