Stuck on a Problem

[Sidharth Khattri]

I'm stuck on a problem. Can anyone please give a hint of how to solve it or please solve this problem. I want to take an input(N) from user and produce the output as follows:

And 0 < N < 101

• For N = 1:

"a", "b", ..., "z".


• For N = 2:

"a", "b", ..., "z",


"aa", "ab", ..., "az",
"ba", "bb", ..., "bz",
.
.
.
"za", "zb", ...,"zz"


• For N = 3:

"a", "b", ..., "z",


"aa", "ab", ..., "az",
"ba", "bb", ..., "bz",
.
.
.
"za", "zb", ...,"zz"


"aaa", "aab", ..., "aaz",
"aba", "abb", ..., "abz"
.
.
.
"baa", "bab", ..., "baz", ...,
.
.
"zaz", "zbz", ..., "zzz".

Since the answer can be quite large I should output it as modulo 1000000007 (10E9 + 7).

How will I loop through these conditions?

[Henry Wong]

Sidharth Khattri wrote:I'm stuck on a problem. Can anyone please give a hint of how to solve it or please solve this problem. I want to take an input(N) from user and produce the output as follows:

And 0 < N < 101

• For N = 3:

"a", "b", ..., "z",


"aa", "ab", ..., "az",
"ba", "bb", ..., "bz",
..
.
"zaz", "zbz", ..., "zzz".

Since the answer can be quite large I should output it as modulo 1000000007 (10E9 + 7).

How will I loop through these conditions?

Well, if N was fixed, the easy answer would be to use nested loops -- meaning for N=3, you will need a loop within a loop within a loop. However, since N is not fixed, then using recursion is probably the best option -- meaning to recursively do the next inner loop until N is reached.

Henry

[Sidharth Khattri]

Hi Henry, I'm having a hard time thinking of solving the problem recursively. I solved it using iteration at first but the input(N) has to be taken from the user. Can you help?

[Henry Wong]

Sidharth Khattri wrote:Hi Henry, I'm having a hard time thinking of solving the problem recursively. I solved it using iteration at first but the input(N) has to be taken from the user. Can you help?

Of course, that is what the ranch is for. Let us know what issues you are having. And what have you done so far. And we can give you some pointers in the right direction.


A word of warning though. How comfortable are you with recursion? Recursion is something that is difficult to teach, even in a classroom setting -- so this will work better if you are already comfortable with it.

Henry