C language games (I) -- guessing games

Catalog

Preface

Guessing judgment

if else sentence

Repeat until you are right （do sentence ,while sentence ）

Set the target number randomly

srand Function shows great magic

Limit the number of times and save the input record

The end of the

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Preface

Law enforcement .C The language games series is expected to have 10 individual , It is more suitable for those who have already learned C Introduction to language , And want to master the actual programming ability of the program ape .

Guessing games should be available in textbooks for beginners , The difficulty coefficient is not big , It belongs to the kind of program that has been done over and over . But even the smallest fly has meat ! In fact, the guessing game also includes Many practical skills . Cut a long story short , Next, listen to the law . Explain to you who are eager to ascend C Language games ( One ）---- Guess the game .

Guessing judgment

Let's start with a beta version “ Guess the game ”. adopt if else sentence 、scanf Function to type a number and “ Target number ” Compare , And show the consequences of comparison .

#include <stdio.h>

int main()
{
	int no;
	int ans = 5;

	printf("Please guess0--9:\n");

	printf(" How much is? ？\n");
	scanf("%d", &no);

	if (no > ans)
		printf("Too big!\n");
	else if (no < ans)
		printf("Too small\n");
	else
		printf("Yes!You are right!\n");     \\    \n Is an escape character , Means line break 

	return 0;
}

The number set up in this game is 5. If the number entered is less than 5, The output Too small！; If the number entered is greater than 5, The output Too big！.

if else sentence

In this procedure if The statement takes the form .

if（ expression ） sentence else if（ expression ） sentence else sentence

Among them else if It can be a lot of , It depends on the number of conditions the programmer wants to design .

Next, we discuss the method of multi - branch , That is to say, the above sentence is more additional 2 Kind of if else Compare morphological statements , Get the pros and cons . Don't talk much , Code up ！

if（no > ans)
    printf("Too big!\n");
else if(no < ans)
    printf("Too small!\n");
else
    printf("Yes!You are right!\n");          //1



if（no > ans)
    printf("Too big!\n");
else if (no < ans)
    printf("Too small!\n");
else if (no == ans)
    printf("Yes!You are right!\n");          //2



if（no > ans)
    printf("Too big!\n");
if (no < ans)
    printf("Too small!\n");
if (no = ans)
    printf("Yes!You are right!\n");          //3

Let's analyze the program 2、3 More in 1 See what conclusions can be drawn . Program 2 Comparison procedure 1 Added （no==ans） Judge , This is actually very redundant Of ; Program 3 One of the three if Juxtaposition , No matter what no and ans How about the size relationship between , The program will judge these three conditions .

Next, we will use charts analysis program 1、2、3 The judgment made , See what conclusions can be drawn . Below 【1】 Judge no>ans,【2】 Judge no<ans,【3】 Judge no==ans.

Size relationship	no>ans when	no<ans when	no==ans when
1	【1】	【1】【2】	【1】【2】
2	【1】	【1】【2】	【1】【2】【3】
3	【1】【2】【3】	【1】【2】【3】	【1】【2】【3】

It can be concluded from the above that , Program 1 Is the most efficient .

Repeat until you are right （do sentence ,while sentence ）

The last program only allowed players to input values once, which was very boring . So we will program improvement once , So that players can Keep typing until you get it right . How can we input multiple times ？ The cycle we learned should come in handy . utilize do Statement loop realizes multiple input , The code is as follows ：

#include <stdio.h>

int main()
{
	int no;
	int ans = 7;

	printf(" Please guess one 0-9 Number of numbers .\n\n");

	do {
		printf(" How much is? ？\n");
		scanf("%d", &no);

		if (no > ans)
			printf("Too big!\n");
		else if (no < ans)
			printf("Too small!\n");
		else
			printf("Yes!You are right!\n");
	} while (no != ans);

	return 0;
}

do The sentence is Cycle first and then judge Of , With its good brother while Statement and for The statements are different （ I'll talk about it later ）. In the application of do Always remember that there is a semicolon at the end of the statement “ ; ” Of . As shown above ,do The control expression of the statement is no!=ans, Operator ！= Judge whether the values of the left and right operands are not equal . If this condition holds , The program will generate int Type 1 It means to continue , If not, it will generate int Type 0 Indicates the end of the cycle .

Next, let's look at using while Statement to realize the guessing game ：

#include <stdio.h>

int main()
{
	int no;
	int ans = 7;

	printf(" Please guess one 0-9 Number of numbers .\n\n");

	while (1) {
		printf(" How much is? ？\n");
		scanf("%d", &no);

		if (no > ans)
			printf("Too big!\n");
		else if (no < ans)
			printf("Too small!\n");
		else
			break;
	}
	printf("Yes!You are right!\n");
	
	return 0;
}

while The sentence is Judge before you cycle , Follow the one in front do The circulation of statements is different . Above ,while The control expression for is 1, So the cycle will go on forever . Isn't this a cycle “ Infinite loop ”？ How to crack such a cycle ？break sentence Great display of magic power , Directly forced out of the loop statement .

Set the target number randomly

In the previous game , It's too boring to guess the number you set yourself , If you can randomly generate numbers to guess, it will increase a lot of interest . Think carefully , It seems that we can use rand function To generate random numbers .rand Its function is to calculate 0-RAND_MAX（ Many beginners don't know RAND_MAX, This is actually a header file <stdlib.h> Contains a macro , It is specified that its value cannot be less than the minimum number specified by the compilation environment , The minimum is 32767） Pseudo random integer sequence of . What is the “ false ”？ Let me analyze them one by one . On the first code :

#include <stdio.h>
#include <stdlib.h>        

int main()
{
	int retry;          // Run again ？

	printf(" In this compilation environment, you can generate 0-%d The random number .\n", RAND_MAX);

	do {
		printf("\n Generated a random number %d.\n", rand());

		printf(" Run again ？  (0) no (1) yes :");
		scanf("%d", &retry);
	} while (retry == 1);

	return 0;
}

Smart friends can do it by themselves ctrl+c Look at the compiler , If you execute the program several times, you will find that the generated random sequence is identical ！rand Functions that seem to generate random are not random , There are certain rules to follow . Why? ？ This is because rand Default seed of function （rand The function is for a called “ seeds ” To generate a random number ） yes 1. If we want to generate different random sequences , You have to change the value of the seed .

srand Function shows great magic

srand Function can solve the dilemma described above . Its function is For subsequent calls rand Function to set a seed , Used to generate a new pseudo-random number sequence . If this function is called with the value of the same seed , The same sequence of pseudo-random numbers will be generated . If you call this function before you call it rand function , It is equivalent to the program calling this function at the beginning , Set the seed to 1, Finally, a seed value of 1 Sequence . Besides , Other library functions will ignore the call of this function at runtime .

How to express ？ For example srand（50） and srand（40）, The random sequences they generate are different , Look at the table below ：

The seed is 50 when , Generate 235->666->777->231->3489.....

The seed is 40 when , Generate 222->2678->2235->1463->87.....

Next, we want to change the seed from a constant to a random value , The header file can be referenced <time.h> Of time（）, This is achieved by using the time when the program is run as a seed . Code up ：

#include <stdio.h>
#include <stdlib.h>
#include <time.h>

int main()
{
	int retry;

	srand(time(NULL));

	printf(" In this compilation environment, you can generate 0-%d The random number .\n", RAND_MAX);

	do {
		printf("\n Generated a random number %d.\n", rand());

		printf(" Run again ？  (0) no (1) yes :");
		scanf("%d", &retry);
	} while (retry == 1);

	return 0;
}

RAND_MAX As mentioned above, the number it generates may be very large , Hundreds of thousands are possible . So how should we control srand Generated random values ？ We can use The remainder To achieve . Popularize it The concept of remainder . Please see the following ：

rand（）%6        Is to generate 0 To 5 The random number , Because the result of the remainder operation will not be greater than the remainder

、 We will modify the above code ：

#include <stdio.h>
#include <stdlib.h>
#include <time.h>

int main()
{
	int retry;

	srand(time(NULL));

	printf(" In this compilation environment, you can generate 0-%d The random number .\n", RAND_MAX);

	do {
		printf("\n Generated a random number %d.\n", rand());

		printf(" Run again ？  (0) no (1) yes :");
		scanf("%d", &retry);
	} while (retry == 1);

	return 0;
}

In this way, the game will not be boring ！ But it's like Lacking a little tension , We should upgrade the program again ---- Limit the number of times and save the input record .

Limit the number of times and save the input record

If the game can limit the number of entries and save the values entered by the player , The game experience of players will be greatly upgraded ！ Think of saving the entered values , We can definitely associate Save with array . adopt Array traversal , Store the values entered by the player one by one , And present it to the player after the game , Let players know how close their guessed number is to the target number . On the first code ：

#include <stdio.h>
#include <stdlib.h>
#include <time.h>

#define MAX_STAGE 10

int main()
{
	int i;
	int stage;           // The number of times the player has operated 
	int no;
	int ans;
	int num[MAX_STAGE];        // The maximum number of times a player can operate 

	srand(time(NULL));
	ans = rand() % 1000;

	printf(" Please guess one 0-999 The integer of .\n\n");

	stage = 0;
	do {
		printf(" And then there were %d Second chance . How much is? ： ", MAX_STAGE - stage);
		scanf("%d", &no);
		num[stage++] = no;

		if (no > ans)
			printf("Too big!\n");
		else if (no < ans)
			printf("Too small!\n");
	} while (no != ans && stage < MAX_STAGE);

	if (no != ans)
		printf(" unfortunately , The right answer is %d.\n", ans);
	else
	{
		printf("Yes!You are right!\n");
		printf(" You used %d I guessed right .\n", stage);
	}

	puts("\n---  Input record  ---");
	for (i = 0; i < stage; i++)
		printf(" %2d:%4d %+4d\n", i + 1, num[i], num[i] - ans);

	return 0;
}

Let's analyze the above code .

（1） Let me start with a wrong example . Beginners often make such mistakes ：

int n=10;
int arr[n]={0};

At first glance, it seems to be similar to the above , But it's actually error Writing . First define a macro , Then in the array 【】 The macro referenced in is correct Writing ;

（2） Code num[stage++]=no; yes After ++, The use of for loop Come on stage Increase the number of . Through repeated cycle processing , The values entered by the player can be stored in the array in order .

（3） In this code, we use the above not mentioned for Statement to Display output records . Let's pull out this code and explain it separately ：

for (i = 0; i < stage; i++)
		printf(" %2d:%4d %+4d\n", i + 1, num[i], num[i] - ans);

First turn on the i The value of the set 0, When i The value is less than stage when , Just keep going i On the value of +1, So that the loop body can run stage Time （stage The value of is equal to the number of times the player enters the value ）.

%2d %4d  The number before the symbol and letter represents their field width , and %+4d Medium +4 Is to align the numbers to the right .

Below · Represents a space , With 125 For example

%4d     125·

%+4d    ·125

The end of the

The above is the law . For the first game in this series ---- Understanding and analysis of word guessing game , Thank you for watching here ！ If you think this blog is helpful to you who are learning programming , Please give me the law . A little more support and attention ！ Next 10 Practice law for many days . We will play other programmed games with you , I hope I can offer you better games next time , I also hope to have you in my next blog ！