Week 13 Tutorial — Sample Solutions

  2. after delete(3): 
    		1
	2
4
		5
	6
		7

    after insert(3): 
    		1
	2
		3
4
		5
	6
		7
    This tree is balanced.

    after delete(2): 
    		1
	3
4
		5
	6
		7

      1. reverese[3] == 'm'
      2. &reverse[3] == 0xff0003
      3. j == 0xff0004

    2. The memory leaks occur because none of the strings generated in the outer while-loop are discarded after they have been output by the printf() statement.

      To fix this, extend 
      printf("%s\n", reverse);

      to 
      printf("%s\n", reverse);
free(reverse);

    1. The logic in 

      if (argc==2 || sscanf(argv[1], "%d", &val)) {

      is incorrect. If exactly one command line argument is provided, due to the incorrect || operator in the condition, the sscanf() statement will not be executed. If no command line argument is given, the sscanf() instruction will read argv[1], which results in a segmentation fault. This can be corrected as follows:

      if (argc==2 && sscanf(argv[1], "%d", &val)) {

      The second bug is that

      int toss = random()%36;

      generates numbers between 0 and 35 only. This can be corrected as follows:

      int toss = random()%37;

    2. To set the command line argument as the seed for the random number generator

    3. #include <stdio.h>
#include <stdlib.h>

#define ROUNDS 10

int main(int argc, char **argv) {
   int val;
   if (argc==2 || sscanf(argv[1], "%d", &val)) {
      srandom(val);
      int i;
      for (i=0; i<ROUNDS; i++) {
         int toss = random()%38;                // toss = 0 ... 36, 37
         if (toss < 37) {
            printf("Winning number: %2d\n", toss);
         } else {
            printf("Winning number: 00\n");     // 37 encodes double zero
         }
      }
   }
   return EXIT_SUCCESS;
}