C语言循环结构与时间函数用法实例教程

/**********************************************
** 《Beginning C 4th Edition》 Notes codes
** Created by Goopand
** Compiler: gcc 4.7.0
***********************************************/
/* Simon games : memory ability test */
#include <stdio.h>       /* for printf(),scanf() function */
#include <ctype.h>       /* for tolower() function */
#include <stdbool.h>      /* for bool type: true, false */
#include <time.h>        /* for time() function */
#include <stdlib.h>       /* for rand(),srand() function */

int main(void)
{
    char nextGame = 'Y';      /* go ahead for another game */
    bool correct = false;      /* guess correctly */
    int counter = 0;        /* number of sequences guessed correctly */
    int seq_len = 0;        /* length of sequence */
    int input_num = 0;       /* stores an input digit */
    time_t seed = 0;        /* seed value for random number sequence */
    //int i = 0;            /* for loop variable */

    clock_t start_clock = 0;    /* record start clock time (not second) */
    int time_taken = 0;       /* Time used for game in seconds */

    printf("Here is a simon game for training memory ability .\n");
    printf("\nThe screen will show a number sequence for 1 second , ");
    printf("then the sequence will disappear. You are suggested to "
        "input the same sequence to pass the game.\n");
    printf("\nNotice this: each digit is seperated by a space. \n");
    printf("\nNow press Enter to play .. Good luck !\n");
    scanf("%c",&nextGame); //Waiting for user's input

    do
    {
        correct = true ;
        counter = 0 ;  /* successful tries */
        seq_len = 2 ;  /* Initial length of a digit sequence */
        time_taken = clock();

        while(correct)
        {
            /* On each third successful try, increase the squence length */
            seq_len += (counter++ % 3 == 0);
            //if "==" expression is true,returns 1; else returns 0

            /* time(NULL) returns number of seconds since 1970-01-01 */
            seed = time(NULL);

            /* Generate and display a sequence of random numbers */
            srand((unsigned int)seed);
            //initialize the seed for rand() function
            for(int i=0; i<seq_len; i++)
                printf("%d ",rand() % 10);
                //Output a random digit and a space

            /* Wait one second */
            start_clock = clock() ;
            //returns start clock time,clock() is a timer
            for(;clock() - start_clock < CLOCKS_PER_SEC;) ;
            //CLOCKS_PER_SEC is a const defined in time.h

            /* Now overwrite the digit sequence */
            printf("\r");
            //control char "\r" : locator back to beginning of the line
            for(int i=0; i<seq_len; i++)
                printf(" ");
                //two spaces to overwrite the sequence
            printf("\r");

            /* Check wether the input sequence is correct */
            srand((unsigned int)seed);   //Restart the random sequence
            for(int i=0; i<seq_len; i++)
            {
                scanf("%d",&input_num); //Read an input number
                if(input_num != rand() % 10 )
                {
                    correct = false ;
                    break;
                }
            }

            printf("%s\n",correct ? "Correct !" : "Wrong !");
        }

        /* Calculate total time to play the game in seconds */
        time_taken=(clock() - time_taken) / CLOCKS_PER_SEC ;

        /* Output the total game score */
        printf("\n\nYour score is %d", --counter * 100 / time_taken);

        fflush(stdin); //Empty the input buffer

        printf("\nDo you want to play again (y/n)? ");
        scanf("%c",&nextGame);
    } while(tolower(nextGame) == 'y');
    return 0;
}