Do-while loop using C -

i'm using while loop per below:

do {      scanf("%c", &turnchoice);      if (turnchoice == 'r')     {         invalidselection = false;     }      else if (turnchoice == 'h')     {         invalidselection = false;     }      else     {         printf("invalid input.\n");     }  } while (invalidselection == true); 

however, before stopping user input, runs full loop once (so displays "invalid input" , asks user letter). doing wrong?

my guess have input before code show, input end newline, right?

the problem here newline still in input-buffer when call scanf read character, newline read , get.

there simple "trick" tell scanf read and discard leading white-space (like newlines), , prepend single space format string, try e.g.

scanf(" %c", &turnchoice); //     ^ //     | // note space here