字符串s2出现在s1的第几个\Debug\vc60.idb
........................\.....\vc60.pdb
........................\.....\wu.exe
........................\.....\wu.ilk
........................\.....\wu.obj
........................\.....\wu.pdb
........................\wu.cpp
........................\wu.dsp
........................\wu.dsw
........................\wu.ncb
........................\wu.opt
........................\wu.plg
........................\Debug
字符串s2出现在s1的第几个