题目,来自牛客网
public class Solution {
public int res = 0;
public int sumNumbers (TreeNode root) {
if (root == null) {
return 0;
}
dfs(root, 0);
return res;
}
public void dfs(TreeNode root, int preSum) {
if (root.left == null && root.right == null) {
res += preSum * 10 + root.val;
return;
}
int res = preSum * 10 + root.val;
if (root.left != null) {
dfs(root.left, res);
}
if (root.right != null) {
dfs(root.right, res);
}
}
}
public class Solution {
public int sumNumbers (TreeNode root) {
if (root == null) {
return 0;
}
return dfs(root, 0);
}
public int dfs(TreeNode root, int preSum) {
if (root == null) {
return 0;
}
if (root.left == null && root.right == null) {
return preSum * 10 + root.val;
}
int curSum = preSum * 10 + root.val;
return dfs(root.left, curSum) + dfs(root.right, curSum);
}
}