生成伪随机整数

#include <stdio.h>
#include <stdlib.h>               // For rand() and srand()
#include <time.h>                 // For time() function

int main(void)
{
  int chosen = 0;                 // The lucky number
  int guess = 0;                  // Stores a guess
  int count = 3;                  // The maximum number of tries
  int limit = 20;                 // Upper limit for pseudo-random values

  srand(time(NULL));              // Use clock value as starting seed
  chosen = 1 + rand() % limit;    // Random int 1 to limit

  for( ; count > 0 ; --count){
    printf("/nYou have %d tr%s left.", count, count == 1 ? "y" : "ies");
    printf("/nEnter a guess: ");  // Prompt for a guess
    scanf("%d", &guess);          // Read in a guess
    // Check for a correct guess
    if(guess == chosen)
    {
      printf("/nYou guessed it!/n");
      return 0;                       // End the program
    }
    else if(guess < 1 || guess > 20)  // Check for an invalid guess
      printf("I said the number is between 1 and 20./n ");
    else
      printf("Sorry, %d is wrong. My number is %s than that./n",
                            guess, chosen > guess ? "greater" : "less");
  }
  printf("/nYou have had three tries and failed. The number was %ld/n",
                                                                 chosen);
  return 0;
}