你说的left应该是leave的过去时吧?
意思完全不同 不可换
leave for 是出发至某处
如:He left for Beijing yesterday.
leave sth for sb 是把什么留给什么人
如：She left these flowers for you.
leave sb for sb 是离开什么人去和什么人在一起
如：He left his wife for a young lady.
leave to 是留某事给...处理
leave sth to do sth 是指为做某事离开某处
如：He left her house to catch the last bus.
leave sb doing sth 是让某人单独做某事
如：Don't leave your children playing with fire.