This is a fun course to try out. I have learnt quite a few things from it and though it may seem to be more geared towards children, adults can join in and will probably find Scratch to be a useful program. I think it brings out the child in everyone of us and it is one of the better edX courses.
Tuesday, May 26, 2015
Monday, May 18, 2015
edX: - HarvardX: CS50x3 Introduction to Computer Science - week 3 Continue
Obama was not totally wrong when it came to answering a Computer Science question.
bubblesort
(n(n-1))/2
big O - eg order of n^2 or O(n^2)
O(n) - finding maximum number in a list
O(log n) -eg phonebook -approximately decreases problem in half every step - list has to be sorted
O(1) - constant
lower bound (n) or Ω(n) - eg bubblesort
lower bound (1) - phonebook
selection sort - upper bound and lower bound of n^2
insertion sort - upper bound and lower bound of n^2
merge sort - eg sort left, sort right and merge O(n log(n)) which is much faster
This work is licensed under a Creative Commons Attribution-NonCommercial 4.0 International License.
bubblesort
(n(n-1))/2
big O - eg order of n^2 or O(n^2)
O(n) - finding maximum number in a list
O(log n) -eg phonebook -approximately decreases problem in half every step - list has to be sorted
O(1) - constant
lower bound (n) or Ω(n) - eg bubblesort
lower bound (1) - phonebook
selection sort - upper bound and lower bound of n^2
insertion sort - upper bound and lower bound of n^2
merge sort - eg sort left, sort right and merge O(n log(n)) which is much faster
This work is licensed under a Creative Commons Attribution-NonCommercial 4.0 International License.
Sunday, May 10, 2015
edX: - HarvardX: CS50x3 Introduction to Computer Science - week 3
Main functions, command line arguments and sorting are covered . There are some fun examples of sorting here.
main with argv[] - array of strings
2 chunks of memory
./hello-3 Zamyla with argv[1]
if no name - null
argv[5000] - segmentation fault - touched segment of memory we should not have
error checking - argc==2
any number of arguments beside 2, program will exit
string - array of char
argv-1 This will print each argument, one per line
argv-2 get the jth char in the string
sorting- bubble sort, selection sort, insertion sort
This work is licensed under a Creative Commons Attribution-NonCommercial 4.0 International License.
2 chunks of memory
./hello-3 Zamyla with argv[1]
if no name - null
argv[5000] - segmentation fault - touched segment of memory we should not have
error checking - argc==2
any number of arguments beside 2, program will exit
string - array of char
argv-1 This will print each argument, one per line
argv-2 get the jth char in the string
sorting- bubble sort, selection sort, insertion sort
This work is licensed under a Creative Commons Attribution-NonCommercial 4.0 International License.
Sunday, May 3, 2015
edX: - HarvardX: CS50x3 Introduction to Computer Science - week 2 Continue
Strings and arrays are covered. At the end is a humorous clip from the movie " Spaceballs".
string - char
strlen needs string.h library
not enough memory
null if something goes wrong
check for null
ASCII
integer to char
capitalize
ctype library functions - toupper and islower
https://reference.cs50.net/ info for functions in libraries
arrays
strings end with \0
This work is licensed under a Creative Commons Attribution-NonCommercial 4.0 International License.
string - char
strlen needs string.h library
not enough memory
null if something goes wrong
check for null
ASCII
integer to char
This work is licensed under a Creative Commons Attribution-NonCommercial 4.0 International License.
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