char c[39]={'0','1','2','3','4','5','6','7','8','9','a','b','c','d','e','f','g','h','i','g','k','l','m','n','o','p','q','r','s','t','u','v','w','x','y','z'};
//用VC++来实现，从C[39]任选一个（可以重复选择），构成一位的、二位的、等等一直到、18位的所有可能的排列输出，实现输出到“*.txt”.