strcmp and strcmpi

Compare Two Strings

Sometimes you want to determine if two strings are the same. For this we have the strcmp function.

int strcmp(string1, string2);

Compare Two Strings (Not Case Sensitive)

If you do not care whether your strings are upper case or lower case then use this function instead of the strcmp function. Other than that, it’s exactly the same.

 printf("%d", strcmp(fname, lname));

Note:stricmp is Windows-specific.

If you're not on Windows, strcasecmp 

Check Leap Year

#include <stdio.h>
int main(){
      int year;
      printf("Enter a year: ");
      scanf("%d",&year);
      if(year%4 == 0)//leap year are multiples of 4
      {
          if( year%100 == 0) /* Checking for a century year */
          {
              if ( year%400 == 0)
                 printf("%d is a leap year.", year);
              else
                 printf("%d is not a leap year.", year);
          }
          else
             printf("%d is a leap year.", year );
      }
      else
         printf("%d is not a leap year.", year);
      return 0;
}

'You can roll a dice three times. You will be given $X where X is the highest roll you get. You can choose to stop rolling at any time (e.g., if you roll a 6 on the first roll, you can stop). What is your expected payout?' -- Facebook Data Scientist interview candidate

Let's suppose we have only 1 roll. What is the expected payoff? Each roll is equally likely, so it will show 1,2,3,4,5,6 with equal probability. Thus their average of 3.5 is the expected payoff.
Now let's suppose we have 2 rolls. If on the first roll, I roll a 6, I would not continue. The next throw would only maintain my winnings of 6 (with 1/6 chance) or make me lose. Similarly, if I threw a 5 or a 4 on the first roll, I would not continue, because my expected payoff on the last throw would be a 3.5. However, if I threw a 1,2 of 3, I would take that second round. This is again because I expect to win 3.5.
So in the 2 roll game, if I roll a 4,5,6, I keep those rolls, but if I throw a 1,2,3, I reroll. Thus I have a 1/2 chance of keeping a 4,5,6, or a 1/2 chance of rerolling. Rerolling has an expected return of 3.5. As the 4,5,6 are equally likely, rolling a 4,5 or 6 has expected return 5. Thus my expected payout on 2 rolls is .5(5)+.5(3.5)=4.25.
Now we go to the 3 roll game. If I roll a 5 or 6, I keep my roll. But now, even a 4 is undesirable, because by rerolling, I'd be playing the 2 roll game, which has expected payout of 4.25. So now the expected payout is 13(5.5)+23(4.25)=4.66¯¯¯¯¯.