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        /* for printf(),scanf() function */ #include        /* for tolower() function */ #include       /* for bool type: true, false */ #include         /* for time() function */ #include        /* 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 t<em style="color:transparent">来源gao.dai.ma.com搞@代*码网</em>hird 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; }