[SOLVED] programming

I’m studying for my Computer Science class and need an explanation.

1. Write a recursive function that prints all permutations of the characters in a string. Your program is to prompt the user with “$>$ ” (note the blank space after the “$>$”). The user then enters a string of letters or digits or both, and the program lists the permutations. It then reprompts the user for a new string. It continues doing this until the user enters either a blank line or types an end-of-file (control-D as the first character).
   Here is an example. The user types what is in red type; what the computer types is in black type. The “%” is a shell prompt. The “?” means the user typed return or enter (or otherwise entered a newline). Your listing of the permutations need not be in the same order, but it must include all permutations of the input.

   > 123?
   123
   231
   312
   132
   213
   321
   > ab?
   ab
   ba
   > ?
   

   To turn in: Put this program into a file called permute.c; turn it in as directed below.

2. (30 points) Throughout the rest of the term, we will build a program to play the game of life, devised by John Conway. It uses a board that is a two-dimensional rectangle divided into small, equal-sized squares. Each square may be populated or unpopulated. The neighbors of a cell are the cells that adjoin it vertically, horizontally, or diagonally.
   At each step, the following transformations are applied to all the cells.
   1. If a populated cell adjoins less than 2 other populated cells, or more than 3 populated cells, it becomes unpopulated.
   2. If a populated cell adjoins 2 or 3 populated cells, it remains populated.
   3. If an unpopulated cell adjoins exactly 3 populated cells, it becomes populated.

   As a first step, you will read the dimensions of the board from the standard input. This will be given as two integers separated by an “x” (the 24th letter of the alphabet) and possibly white space before and after the numbers and the “x”. Your output is to be a square composed of “-”es and “|”es. If the numbers read are “2 x 8”, your square should enclose a 2×8 rectangle. The inside of the rectangle is to be blank.
   To turn in: Put this program into a file called life.c; turn it in as directed below. If you want to submit two files, that is, have this in a separate file, call the main one life.c and the other file(s) readrectn.c, where n is a single digit (for example, readrect0.c). Turn it in as described below.