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;}