原始字符串是"abc"，打印得到下列所有组合情况：
*"a" "b" "c"
*"ab" "bc" "ca" "ba" "cb" "ac"
*"abc" "acb" "bac" "bca" "cab" "cba"
思路什么么

原始字符串是"abc"，打印得到下列所有组合情况：
*"a" "b" "c"
*"ab" "bc" "ca" "ba" "cb" "ac"
*"abc" "acb" "bac" "bca" "cab" "cba"
思路什么么