LeetCode p404 Sum of Left Leaves 题解
1.题目：
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.
题意：
输入一个二叉树，输出所有左节点的累加和。
2.解题思路:
这里的左节点指左右节点都为空的左节点。
3.代码
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public class {
public int sumOfLeftLeaves(TreeNode root) {
if (root == null)
return 0;
if (root.left == null)
return sumOfLeftLeaves(root.right);
if (root.left.left == null && root.left.right == null)
return root.left.val + sumOfLeftLeaves(root.right);
return sumOfLeftLeaves(root.left) + sumOfLeftLeaves(root.right);
}
}
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4.一些总结：
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