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ecs30 Winter 2012: Programming and Problem Solving Final Review

ecs30 Winter 2012: Programming and Problem Solving Final Review. Dr. S. Felix Wu Computer Science Department University of California, Davis http://www.cs.ucdavis.edu/~wu/ wu@cs.ucdavis.edu. Final. About 50~75% from the two midterms Similar concepts, more mixings

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ecs30 Winter 2012: Programming and Problem Solving Final Review

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  1. ecs30 Winter 2012:Programming and Problem SolvingFinal Review Dr. S. Felix Wu Computer Science Department University of California, Davis http://www.cs.ucdavis.edu/~wu/ wu@cs.ucdavis.edu ecs30 Winter 2012 final review

  2. Final • About 50~75% from the two midterms • Similar concepts, more mixings • Everything should be within “slides” • But, with extensions • Chapters 2~6, 8~12, 14 plus slides • Please, after the quarter, read 7 & 13. • Focusing on Problem solving in C! ecs30 Winter 2012 final review

  3. ecs30 Winter 2012 final review

  4. 0 = 0000 = 0 * 8 + 0 * 4 + 0 * 2 + 0 * 1 1 = 0001 = 0 * 8 + 0 * 4 + 0 * 2 + 1 * 1 2 = 0010 = 0 * 8 + 0 * 4 + 1 * 2 + 0 * 1 3 = 0011 = 0 * 8 + 0 * 4 + 1 * 2 + 1 * 1 ....... 7 = 0111 = 0 * 8 + 1 * 4 + 1 * 2 + 1 * 1 8 = 1000 = 1 * 8 + 0 * 4 + 0 * 2 + 0 * 1 9 = 1001 = 1 * 8 + 0 * 4 + 0 * 2 + 1 * 1 10 (a) = 1010 = 1 * 8 + 0 * 4 + 1 * 2 + 0 * 1 11 (b) = 1011 = 1 * 8 + 0 * 4 + 1 * 2 + 1 * 1 12 (c) = 1100 = 1 * 8 + 1 * 4 + 0 * 2 + 0 * 1 13 (d) = 1101 = 1 * 8 + 1 * 4 + 0 * 2 + 1 * 1 14 (e) = 1110 = 1 * 8 + 1 * 4 + 1 * 2 + 0 * 1 15 (f) = 1111 = 1 * 8 + 1 * 4 + 1 * 2 + 1 * 1 Examples: 09FE (in Hex) == ? (in Binary) == ? (in Decimal) ecs30 Winter 2012 final review

  5. T * = (int) * T* xp; <type> * <variable name>; I declare a variable xp such that xp is an address containing a T-type object. address xp &xp x T(int) = 222 x (*xp) == 222; ecs30 Winter 2012 final review

  6. T * = (int) * T* xp; <type> * <variable name>; I declare a variable x such that x is an address containing a T-type object. xp = &x; 34ef5f12 xp &xp &x == 0x34ef5f12 T(int) = 222 x x == 222 *xp == 222 ecs30 Winter 2012 final review

  7. printf(“%lf\n”, &miles); printf(“%lf\n”, miles); printf(“%lf\n”, 0x7014ae00); printf(“%lf\n”, 30.5); printf(“%lf\n”, *(&miles)); printf(“%lf\n”, *((double *) 0x7014ae00); 8 bytes 0x 7014ae00 0x 7014ae01 0x 7014ae02 0x 7014ae03 0x 7014ae04 0x 7014ae05 0x 7014ae06 0x 7014ae07 In C, Pointer = Address + Type! And, Address is merely a 32 bit unsigned integer! ecs30 Winter 2012 final review

  8. “Type” gives the semantic meaning of an address! $ ./a.out char = bffffa09 int = bffffa0c func = 1f62 func = 1f63 size = 4 #include <stdio.h> #include <stdlib.h> int main (void) { intx = 222; unsigned char*ptr_uchar = (unsigned char *)&x; printf(“char = %x\n”, (((char *) ptr_uchar) + 1)); printf(“int = %x\n”, (((int *) ptr_uchar) + 1)); /* pointer to function being casted */ ptr_uchar=(unsigned char *) main; printf(“func = %x\n”, (((int (*)(void)) ptr_uchar))); printf(“func = %x\n”, (((int (*)(void)) ptr_uchar) + 1)); printf(“size = %d\n”, sizeof(int (*)(void))); } ecs30 Winter 2012 final review

  9. *(ap + i) is the actual implementation of ap[i]! 0x000000de ?? 0x000000df • int x = 222; • &x • *x • *(&x) • *(((char *) ap) + 1) • *(((int *) ap) + 1) • *(((platnet_t *) ap) + 1) 0x000000e0 0x000000e1 0xbffffa08 222 0xbffffa09 0xbffffa0a 0xbffffa0b 0xbffffa0c ecs30 Winter 2012 final review

  10. addition ((type *) xp + k) == The value of address xp + sizeof(type) * k (int **) ~ ((int *) *) ~ type == (int *) ((type *) xp + k) == The value of address xp + sizeof((int *)) * k ecs30 Winter 2012 final review

  11. trouble.c (hw#2)(try to control the input) #include <stdio.h> int main(void) { int x; printf("%x\n", &x); printf("%d\n", (int) &x); scanf("%d", &x); printf("[04] %d\n", (int) *((int *) x)); } What would be the valid input values for x such that the program won’t crash? ecs30 Winter 2012 final review

  12. num_1 X num_2 n Call by Reference &num_1 &x &num_2 &n num_1 num_2 ecs30 Winter 2012 final review

  13. #include <stdio.h> int main(void) { int rc; int num[3]; num[0] = 107; num[-20005675] = 105; printf("%x\n", num[0]); printf("%x\n", (unsigned int) *num); printf("%x\n", (unsigned int) &(num[0])); printf("%x\n", (unsigned int) &(num[1])); printf("%x\n", (unsigned int) &(num[2])); printf("%x\n", (unsigned int) &(num[-1])); printf("%x\n", (unsigned int) &(num[3])); printf("%x\n", (unsigned int) &num); printf("%x\n", (unsigned int) num); printf("%d\n", num[-20005675]); return 0; } ecs30 Winter 2012 final review

  14. 0,0 0,1 0,2 0,3 int I_array[4][4]; char C_array[4][4]; 1,0 1,1 1,2 1,3 2,0 2,1 2,2 2,3 void printMatrix (char m[][]) { m[2][1] … } 3,0 3,1 3,2 3,3 I_array == &(I_array[0][0]) m[x][y] ~ *((char *) m + x*columns + y) 0,0 0,1 0,2 0,3 1,0 1,1 1,2 1,3 2,0 2,1 2,2 2,3 3,0 3,1 3,2 3,3 How many rows I should skip? ecs30 Winter 2012 final review

  15. 0,0 0,1 0,2 0,3 char m[4][4]; 1,0 1,1 1,2 1,3 void printMatrix (char m[][4]) { m[2][1] … } 2,0 2,1 2,2 2,3 3,0 3,1 3,2 3,3 m == &(m[0][0]) m[x][y] ~ *((char *) m + x*columns + y) 0,0 0,1 0,2 0,3 1,0 1,1 1,2 1,3 2,0 2,1 2,2 2,3 3,0 3,1 3,2 3,3 How many rows I should skip? ecs30 Winter 2012 final review

  16. 0,0 0,1 0,2 0,3 char m[4][4]; 1,0 1,1 1,2 1,3 void printMatrix (char m[][4]) { m[2][1] … } 2,0 2,1 2,2 2,3 3,0 3,1 3,2 3,3 m == &(m[0][0]) &(m[x][y]) ~ ((char *) m + x*columns + y) 0,0 0,1 0,2 0,3 1,0 1,1 1,2 1,3 2,0 2,1 2,2 2,3 3,0 3,1 3,2 3,3 How many rows I should skip? ecs30 Winter 2012 final review

  17. num[0] num[1] num[2] (4 bytes) (4 bytes) (4 bytes) num[0] int num[N]; printf(“%x\n”, num); num[1] Equivalence between int num[]; and int *num; num[2] ecs30 Winter 2012 final review

  18. m[x][y] ~ *((char *) m + x*columns + y) ((int) m) + ((x*columns) + y) * sizeof(char) m[x][y] ~ *((int *) m + x*columns + y) ((int) m) + ((x*columns) + y) * sizeof(int) ecs30 Winter 2012 final review

  19. The end of a string ecs30 Winter 2012 final review

  20. int strlen(char *s) { int i = 0; while (s[i++] != ‘\0’); return (i-1); } fprintf(stdout, “output: %d\n”, strlen(string_var)); output: 13 * * * * * E r r o r ‘ ‘ - ‘ ‘ \0 string_var ecs30 Winter 2012 final review

  21. #include <stdio.h> #include <string.h> int main(void) { char dest_s[20]; char src_s[20] = “Jan. 30, 1996”; strncpy(dest_s, src_s, 9); fprintf(stdout, “%s\n”, dest_s); return 0; } ecs30 Winter 2012 final review

  22. #include <stdio.h> #include <string.h> int main(void) { char dest_s[20]; char src_s[20] = “Jan. 30, 1996”; fprintf(stdout, “%s\n”, strncpy(dest_s, src_s, 9)); return 0; } ecs30 Winter 2012 final review

  23. ‘U’ ‘C’ ‘ ’ ‘\0’ ? ? ? ? ? s1 ‘D’ ‘a’ ‘v’ ‘i’ ‘s’ ‘\0’ ? ? ? s2 ‘U’ ‘C’ ‘ ’ ‘D’ ‘a’ ‘v’ ‘i’ ‘s’ ‘\0’ s1 strcat(s1, s2); ecs30 Winter 2012 final review

  24. #include <stdio.h> #include <string.h> int main(void) { char s1[9] = “UC “; char s2[9] = “Davis”; fprintf(stdout, “%d\n”, strcmp(s1, s2)); return 0; } ecs30 Winter 2012 final review

  25. #include <stdio.h> #include <string.h> int strcmp(char *s1, char *s2) { } ecs30 Winter 2012 final review

  26. Strings • strcpy, strncpy, strdup, strcmp ecs30 Winter 2012 final review

  27. char * strdup(char *s) { return strcpy( (char *) malloc(sizeof(char) *(strlen(s) + 1)), s); } ecs30 Winter 2012 final review

  28. malloc & free • malloc: • Input: the size of the memory cells • return: the address of the first memory cell #include <stdlib.h> void *xp; xp = malloc(sizeof(planet_t)); ecs30 Winter 2012 final review

  29. malloc & free • free: • Input: an address • return: nothing #include <stdlib.h> void *xp; xp = malloc(sizeof(planet_t)); free(xp); ecs30 Winter 2012 final review

  30. int *ip; ip = (int *) malloc(sizeof(int)); double *dp; dp = (double *) malloc(sizeof(double)); ecs30 Winter 2012 final review

  31. Game of Life int Array[25][25]; int **a_ptr = NULL; n = 25; a_ptr = (int **) malloc(sizeof(int) * n * n); ecs30 Winter 2012 final review

  32. Recursion It gotta stop… at some point!! Exit Strategy/Condition! ecs30 Winter 2012 final review

  33. tower3p Big ==8 Small == 1 ecs30 Winter 2012 final review

  34. from to Big == 5 Small == 1 Big == 8 Small == 6 ecs30 Winter 2012 final review

  35. Logic • Move the top part using 4 pegs • From > Aux2 • Move the bottom part using 3 pegs • From > To • Move the top part using 4 pegs • Aux2 > To ecs30 Winter 2012 final review

  36. Exit Condition ecs30 Winter 2012 final review

  37. int movecount = 1; void tower3p (char from_peg, char to_peg, char aux_peg, int big, int small) { if (big == small) { fprintf(stdout, "[%16d] ==> move disk %3d from %c to %c\n", movecount++, big, from_peg, to_peg); } else { tower3p(from_peg, aux_peg, to_peg, big-1, small); fprintf(stdout, "[%16d] ==> move disk %3d from %c to %c\n", movecount++, big, from_peg, to_peg); tower3p(aux_peg, to_peg, from_peg, big-1, small); } } ecs30 Winter 2012 final review

  38. #define STRSIZ 10 struct planet { char name[STRSIZ]; double diameter; int moons; double orbit_time, rotation_time; struct planet *next; struct planet *previous; }; sizeof(struct planet) == ? ecs30 Winter 2012 final review

  39. printf("%d\n", ((planet_t *) 0)->diameter); ecs30 Winter 2012 final review

  40. #define STRSIZ 10 typedef struct { char name[STRSIZ]; double diameter; int moons; double orbit_time, rotation_time; } planet_t; printf("%d\n", (int) &(((planet_t *) 0)->name)); printf("%d\n", (int) &(((planet_t *) 0)->diameter)); printf("%d\n", (int) &(((planet_t *) 0)->moons)); Expect: 0, 10, 18 MacBook/pc16 (i386): 0, 12, 20 pc26 (x86_64): 0, 16, 24 ecs30 Winter 2012 final review

  41. typedef struct { char name[10]; double diameter; int moons; double orbit_time, rotation_time; } planet_t; &((planet_t *) 0)->diameter) “Be very careful! It’s Machine-Dependent actually!!” ecs30 Winter 2012 final review

  42. I386 architecture typedef struct { char name[10]; double diameter; int moons; double orbit_time, rotation_time; } planet_t; ecs30 Winter 2012 final review

  43. #define STRSIZ 10 typedef struct { char name[STRSIZ]; double diameter; int moons; double orbit_time, rotation_time; } planet_t; … planet_t current_planet[12]; fwrite(current_planet, sizeof(planet_t), 12, planetFile); fread(current_planet, sizeof(planet_t), 12, planetFile); ecs30 Winter 2012 final review

  44. typedef struct { double diameter; int moons; char name[10]; double orbit_time, rotation_time; char tail[2]; } planet_t; sizeof(planet_t) == ? ecs30 Winter 2012 final review

  45. typedef struct { double diameter; int moons; char name[10]; double orbit_time, rotation_time; char tail[2]; char tail2; } planet_t; sizeof(planet_t) == ? ecs30 Winter 2012 final review

  46. fwrite/fread Table 12.5 Pages 625~626 • format versus binary #include <stdio.h> size_t fread(void *restrict ptr, size_t size, size_t nitems, FILE *restrict stream); size_t fwrite(const void *restrict ptr, size_t size, size_t nitems, FILE *restrict stream); ecs30 Winter 2012 final review

  47. 2 1 byte File 1 byte 3 fopen(,) 1 FILE * 4 ecs30 Winter 2012 final review

  48. /usr/include/stdio.h typedef struct __sFILE { unsigned char *_p; /* current position in (some) buffer */ int _r; /* read space left for getc() */ int _w; /* write space left for putc() */ short _flags; /* flags, below; this FILE is free if 0 */ short _file; /* fileno, if Unix descriptor, else -1 */ struct __sbuf _bf;/* the buffer (at least 1 byte, if !NULL) */ int _lbfsize; /* 0 or -_bf._size, for inline putc */ /* operations */ void *_cookie; /* cookie passed to io functions */ int (*_close)(void *); int (*_read) (void *, char *, int); fpos_t (*_seek) (void *, fpos_t, int); int (*_write)(void *, const char *, int); /* separate buffer for long sequences of ungetc() */ struct __sbuf _ub; /* ungetc buffer */ … } FILE; ecs30 Winter 2012 final review

  49. ecs30 Winter 2012 final review

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