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CS50 Lecture2
- 1. This is CS50
- 3. This is CS50
- 5. #include <stdio.h> int main(void) { printf("hello, worldn"); }
- 6. #include <stdio.h> int main(void) { printf("hello, worldn"); }
- 7. #include <stdio.h> int main(void) { printf("hello, worldn"); }
- 8. 01111111 01000101 01001100 01000110 00000010 00000001 00000001 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000010 00000000 00111110 00000000 00000001 00000000 00000000 00000000 10110000 00000101 01000000 00000000 00000000 00000000 00000000 00000000 01000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 11010000 00010011 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 01000000 00000000 00111000 00000000 00001001 00000000 01000000 00000000 00100100 00000000 00100001 00000000 00000110 00000000 00000000 00000000 00000101 00000000 00000000 00000000 01000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 01000000 00000000 01000000 00000000 00000000 00000000 00000000 00000000 01000000 00000000 01000000 00000000 00000000 00000000 00000000 00000000 11111000 00000001 00000000 00000000 00000000 00000000 00000000 00000000 11111000 00000001 00000000 00000000 00000000 00000000 00000000 00000000 00001000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000011 00000000 00000000 00000000 00000100 00000000 00000000 00000000 00111000 00000010 00000000 00000000 00000000 00000000 00000000 00000000 ...
- 10. clang -o hello hello.c ./hello
- 12. #include <stdio.h> int main(void) { printf("hello, worldn"); }
- 13. #include <cs50.h> #include <stdio.h> int main(void) { string name = get_string("Name: "); printf("hello, %sn", name); }
- 16. clang -o hello hello.c -lcs50 ./hello
- 18. compiling
- 21. #include <cs50.h> #include <stdio.h> int main(void) { string name = get_string("Name: "); printf("hello, %sn", name); }
- 22. #include <cs50.h> #include <stdio.h> int main(void) { string name = get_string("Name: "); printf("hello, %sn", name); }
- 23. string get_string(string prompt); #include <stdio.h> int main(void) { string name = get_string("Name: "); printf("hello, %sn", name); }
- 24. string get_string(string prompt); #include <stdio.h> int main(void) { string name = get_string("Name: "); printf("hello, %sn", name); }
- 25. string get_string(string prompt); int printf(const char *format, ...); int main(void) { string name = get_string("Name: "); printf("hello, %sn", name); }
- 26. ... string get_string(string prompt); int printf(const char *format, ...); ... int main(void) { string name = get_string("Name: "); printf("hello, %sn", name); }
- 28. ... string get_string(string prompt); int printf(const char *format, ...); ... int main(void) { string name = get_string("Name: "); printf("hello, %sn", name); }
- 29. ... main: # @main .cfi_startproc # BB#0: pushq %rbp .Ltmp0: .cfi_def_cfa_offset 16 .Ltmp1: .cfi_offset %rbp, -16 movq %rsp, %rbp .Ltmp2: .cfi_def_cfa_register %rbp subq $16, %rsp xorl %eax, %eax movl %eax, %edi movabsq $.L.str, %rsi movb $0, %al callq get_string movabsq $.L.str.1, %rdi movq %rax, -8(%rbp) movq -8(%rbp), %rsi movb $0, %al callq printf ...
- 30. ... main: # @main .cfi_startproc # BB#0: pushq %rbp .Ltmp0: .cfi_def_cfa_offset 16 .Ltmp1: .cfi_offset %rbp, -16 movq %rsp, %rbp .Ltmp2: .cfi_def_cfa_register %rbp subq $16, %rsp xorl %eax, %eax movl %eax, %edi movabsq $.L.str, %rsi movb $0, %al callq get_string movabsq $.L.str.1, %rdi movq %rax, -8(%rbp) movq -8(%rbp), %rsi movb $0, %al callq printf ...
- 31. ... main: # @main .cfi_startproc # BB#0: pushq %rbp .Ltmp0: .cfi_def_cfa_offset 16 .Ltmp1: .cfi_offset %rbp, -16 movq %rsp, %rbp .Ltmp2: .cfi_def_cfa_register %rbp subq $16, %rsp xorl %eax, %eax movl %eax, %edi movabsq $.L.str, %rsi movb $0, %al callq get_string movabsq $.L.str.1, %rdi movq %rax, -8(%rbp) movq -8(%rbp), %rsi movb $0, %al callq printf ...
- 34. ... main: # @main .cfi_startproc # BB#0: pushq %rbp .Ltmp0: .cfi_def_cfa_offset 16 .Ltmp1: .cfi_offset %rbp, -16 movq %rsp, %rbp .Ltmp2: .cfi_def_cfa_register %rbp subq $16, %rsp xorl %eax, %eax movl %eax, %edi movabsq $.L.str, %rsi movb $0, %al callq get_string movabsq $.L.str.1, %rdi movq %rax, -8(%rbp) movq -8(%rbp), %rsi movb $0, %al callq printf ...
- 37. hello.c
- 38. hello.c cs50.c
- 57. array
- 58. string
- 59. input → → output
- 60. plaintext → → ciphertext
- 61. H I !
- 62. 72 73 33
- 66. plaintext → → ciphertext
- 67. plaintext → → ciphertext key →
- 68. plaintext → → ciphertext 1 →
- 69. I L O V E Y O U
- 70. 73 L O V E Y O U
- 71. 73 76 O V E Y O U
- 72. 73 76 79 V E Y O U
- 73. 73 76 79 86 E Y O U
- 74. 73 76 79 86 69 Y O U
- 75. 73 76 79 86 69 89 O U
- 76. 73 76 79 86 69 89 79 U
- 77. 73 76 79 86 69 89 79 85
- 78. 74 76 79 86 69 89 79 85
- 79. 74 77 79 86 69 89 79 85
- 80. 74 77 80 86 69 89 79 85
- 81. 74 77 80 87 69 89 79 85
- 82. 74 77 80 87 70 89 79 85
- 83. 74 77 80 87 70 90 79 85
- 84. 74 77 80 87 70 90 80 85
- 85. 74 77 80 87 70 90 80 86
- 86. J 77 80 87 70 90 80 86
- 87. J M 80 87 70 90 80 86
- 88. J M P 87 70 90 80 86
- 89. J M P W 70 90 80 86
- 90. J M P W F 90 80 86
- 91. J M P W F Z 80 86
- 92. J M P W F Z P 86
- 93. J M P W F Z P V
- 96. #include <stdio.h> int main(int argc, string argv[]) { ... }
- 97. #include <stdio.h> int main(int argc, string argv[]) { ... }
- 98. #include <stdio.h> int main(int argc, string argv[]) { ... }
- 103. Bubble Sort
- 104. repeat until no swaps for i from 0 to n-2 if i'th and i+1'th elements out of order swap them
- 105. Selection Sort
- 106. for i from 0 to n-1 find smallest element between i'th and n-1'th swap smallest with i'th element
- 107. (n – 1)
- 108. (n – 1) + (n – 2)
- 109. (n – 1) + (n – 2) + ... + 1
- 110. (n – 1) + (n – 2) + ... + 1 n(n – 1)/2
- 111. (n – 1) + (n – 2) + ... + 1 n(n – 1)/2 (n2 – n)/2
- 112. (n – 1) + (n – 2) + ... + 1 n(n – 1)/2 (n2 – n)/2 n2 /2 – n/2
- 113. (n – 1) + (n – 2) + ... + 1 n(n – 1)/2 (n2 – n)/2 n2 /2 – n/2 O(n2 )
- 114. n2 /2 – n/2
- 115. n2 /2 – n/2 1,000,0002 /2 – 1,000,000/2
- 116. n2 /2 – n/2 1,000,0002 /2 – 1,000,000/2 500,000,000,000 – 500,000
- 117. n2 /2 – n/2 1,000,0002 /2 – 1,000,000/2 500,000,000,000 – 500,000 499,999,500,000
- 118. n2 /2 – n/2 1,000,0002 /2 – 1,000,000/2 500,000,000,000 – 500,000 499,999,500,000 O(n2 )
- 119. O(n2 ) O(n log n) O(n) O(log n) O(1)
- 121. O(n) O(log n)
- 122. Ω(n2 ) Ω(n log n) Ω(n) Ω(log n) Ω(1)
- 123. Θ(n2 ) Θ(n log n) Θ(n) Θ(log n) Θ(1)
- 124. Merge Sort
- 125. on input of n elements if n < 2 return else sort left half of elements sort right half of elements merge sorted halves
- 127. This is CS50