ECE 15 Lab 3 Match and Hit

The famous Match&Hit game is played by a computer and a human player as follows. First, the com- puter selects a random 4-digit number N = a·103+b·102+c·10+d, where a,b,c,d are distinct non- zero digits — that is, a,b,c,d are distinct elements of the set {1,2,3,4,5,6,7,8,9}. Let us call num- bers like this valid. The human player then tries to deduce N from a sequence of queries to the com- puter. Each query consists of a valid 4-digit number M = x·103+ y·102+ z·10 + w. The computer responds to each query with the number of matches and the number of hits. A match is a digit of N that appears in M at the same position (thus each of x = a, y = b, z = c, or w = d counts as one match). A hit is a digit of N that appears in M, but not at the same position. For example, if N = 5167, then the queries 2934, 1687, 7165, 5167 will result in the following numbers of matches and hits: See image.

where matches are denoted by • and hits are denoted by ◦. The play continues until the human player either wins or loses the game, as follows:

• Human player wins if he submits a query with 4 matches (that is, M = N).
• Human player loses if he submits 12 queries, none of them with 4 matches.

WriteaCprogram, calledmatch and hit.c,thatimplements(thecomputerpartof)theMatch&Hit game. In this program, you are required to declare, define, and call the following functions:

• The function isvalid(int n) that accepts as a parameter an arbitrary integer. The function should return 1 if the integer is valid, and 0 otherwise. Recall that an integer is valid if it is posi- tive, consists of exactly 4 decimal digits, and all these digits are nonzero and distinct.
• The function choose N(void) that returns, as an int, a uniformly random choice of a valid integer N. The function should call both the rand library function and the function isvalid. It should keep calling rand until the number generated thereby is valid. Recall that before the function rand is invoked, the random seed should be initialized using srand(time(0)).
• The function matches(int N, int M) that accepts as parameters two integers N and M and returns, as an int, the number of matches. You can assume than both N and M are valid.
• The function hits(int N, int M) that accepts as parameters two integers N and M, then returns, as an int, the number of hits. You can assume than both N and M are valid.

Here is a sample run of this program, assuming that the executable file is called match and hit. This run illustrates a situation where the human player wins the game. User input is underlined.

/home/userXYZ/ECE15/Lab3> match and hit
***Welcome to the MATCH and HIT game***
The computer has selected a 4-digit number.
Try to deduce it in 12 rounds of queries.
Round #1
Please enter your query (4 digits): 5341
-> 2 matches and 1 hit
Round #2
Please enter your query (4 digits): 1235
-> 1 match and 2 hits
Round #3
Please enter your query (4 digits): 2345
-> 4 matches and 0 hits
**********************************
CONGRATULATIONS! You won the game!
**********************************

Notice that a singular form (match, hit) is used with the number 1. You can easily achieve this func- tionality with the ?: conditional expression, as shown in class. The next sample run illustrates a sit- uation where the human player loses the game. Again, user input is underlined.

/home/userXYZ/ECE15/Lab3> match and hit
***Welcome to the MATCH and HIT game***
The computer has selected a 4-digit number.
Try to deduce it in 12 rounds of queries.
Round #1
Please enter your query (4 digits): 1234
-> 0 matches and 3 hits
..
..
Round #12
Please enter your query (4 digits): 2435
-> 2 matches and 2 hits
*********************************
Sorry, out of queries. Game over!
*********************************

Notes:

• Iftheuserentersanon-integer,printthemessage “Invalid query. Please try again!” Noticethat ifthe user enters an integerfollowed by nonintegercharacters, these characters should be simply ignored (check the value returned by the scanf function). If the user enters an integer that is not valid, print the message “Invalid number. Please try again!” In both of these cases, you should then prompt the user to enter another query, and keep doing so until the user provides a valid input. The following sample run illustrates all this.

/home/userXYZ/ECE15/Lab3> match and hit
***Welcome to the MATCH and HIT game***
The computer has selected a 4-digit number.
Try to deduce it in 12 rounds of queries.
Round #1
Please enter your query (4 digits): ##
Invalid query. Please try again!
Please enter your query (4 digits): 0##
Invalid number. Please try again!
Please enter your query (4 digits): -5341
Invalid number. Please try again!
Please enter your query (4 digits): 123456789
Invalid number. Please try again!
Please enter your query (4 digits): 5340
Invalid number. Please try again!
Please enter your query (4 digits): 5344
Invalid number. Please try again!
Please enter your query (4 digits): 5341#OK?
-> 2 matches and 1 hit
Round #2
Please enter your query (4 digits): 1235
-> 1 match and 2 hits
Round #3
Please enter your query (4 digits): 2345
-> 4 matches and 0 hits
**********************************
CONGRATULATIONS! You won the game!
**********************************

• The maximum numberof queries (which we have, so far, assumed to be 12) should be introduced as a symbolic constant MAX QUERIES in the beginning of the program, using the #define compiler directive. The number of digits in a valid integer (which we have, so far, assumed to be 4) should be also introduced as a symbolic constant called N DIGITS. You can assume that N DIGITS is one of 1,2,3,4 and MAX QUERIES is an integer in the range 1,2,...,24. The program should keep working correctly for all such values of N DIGITS and MAX QUERIES.
• You can always win the game with at most 12 queries, if you query cleverly. Try it, it’s fun! Can you guarantee a win with less than 12 queries? If so, what is the minimum number of queries you need? You do not need to answer these questions, but you are welcome to consider them.