题目404. Sum of Left Leaves
Find the sum of all left leaves in a given binary tree.
Example:
3
/
9 20
/
15 7
There are two left leaves in the binary tree, with values 9 and 15 respectively. Return 24.
1,深搜
public class Solution {
public int sumOfLeftLeaves(TreeNode root) {
return dfs(root) ;
}
private int dfs(TreeNode root){
if(root == null){
return 0;
}
if(root.left == null && root.right == null){
return 0;
}
if(root.left != null && root.left.left == null && root.left.right == null){
return root.left.val+ dfs(root.right);
}
return dfs(root.left) + dfs(root.right);
}
}
