404. Sum of Left Leaves 404.左叶总和

Posted 2021-02-18 immiao0319

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.

不是计算么，怎么变成recursive。好吧，还是在外面，还是算DC,就是直接拿来计算了。计算题直接拿来计算就行了。
“最左边”这个特质就是左边无、右边也无了。好吧，不说我还真看不出来。

都要加到sum上去才行