设T是一个有<img src="http://jgxm-question.oss-cn-beijing.aliyuncs.com/psst/files/7bbcfaeaa8f64fa1b3e4bffdd1afdf43.png?x-oss-process=image/sharpen,200"/>个叶子的二元树，出度为2的顶点为<img src="http://jgxm-question.oss-cn-beijing.aliyuncs.com/psst/files/8876b1ffc0bc46c78b1c4b5028e76ddf.png?x-oss-process=image/sharpen,200"/>,则<img src="http://jgxm-question.oss-cn-beijing.aliyuncs.com/psst/files/ab50570100be422b9f9cd0b2d04267dc.png?x-oss-process=image/sharpen,200"/>。