Questions tagged [week2]

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pset2 mathematical IF statement : attempt

#include <stdio.h> #include <string.h> #include <string.h> #include <stdlib.h> #include <math.h> #include <ctype.h> #include <cs50.h> int main ( int argc, ...
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1answer
64 views

Can I reset all my progress for Week 2 in cs50 IDE?

I am starting the Hello project for cs50 and I made a small mistake in my starting code. In attempting to fix my error, I dug myself deeper into a hole (or a chasm) of mistakes. I think it would be ...
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1answer
17 views

Week 2 Lecture - Functions - Valid Triangle

This is from the functions lecture on a valid triangle. I'm not getting any error messages but I can't figure out why the bool valid_triangle (float x, float y, float z) function is not working. Any ...
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1answer
16 views

Week 2 passing array example problem?

Hi, I have problem understanding the concept of 'passing an array by reference instead of value' and I cant understand this example. Can anyone explain to me why does it take 10, 22 as final answer?
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49 views

Encrypt plaintext in substution.c

Here is my encryption of plaintext after validation the key. //Encrypt Code string plaintext = get_string("plaintext: "); // int array[26] = {0}; string encText = plaintext; //converts user ...
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1answer
26 views

Expected expression on “valid triangle” exercise? i thought the 'or' symbol was 2 lines ( || ) what have i done wrong here?

#include <stdio.h> #include <cs50.h> #include <string.h> #include <ctype.h> #include <math.h> // PROTOTYPE THE FUNCTON bool valid_triangle(float input1, float input2, ...
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2answers
26 views

Can anyone tell me what ive done wrong and breakdown how to properly prototype and deploy created functions?

code: #include <stdio.h> #include <cs50.h> #include <string.h> #include <ctype.h> #include <math.h> // PROTOTYPE THE FUNCTONS & DECLARE VARIABLES int multiply(int ,...
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0answers
21 views

Week2 Help50 Make Buggy0 doesn't work

I executed help50 just like in the lecture(see photo) but it doesn't recognise the file although it is written right:
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1answer
89 views

[Week 2 Substitution.Why does my code fail the checks even if the output is correct?

Here is my code. Apologies if it is hard to understand / messy. When I check50 it shows this. I have a brief idea on how to solve the invalid characters in key but I don't mind some help on that too. ...
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1answer
19 views

Pset 2 Vigenere - Shift value

I am at the point in pset2 Vinegere, where I have to write the shift function. The tutorial (or guidance on the left side in sandbox) is telling me to place the following line of code after the curled ...
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3answers
36 views

Why are algorithms mentioned in week 2

In week 2 David mentions Algorithms e.g. Bubble sort, Binary search etc... But why are they important? and where do they fit into the bigger picture? I only did the Caesar cypher and Vigenere cypher ...
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1answer
118 views

pset3 Music design and connection to Week 2 lecture?

I have completed all of the work for pset3 Music and it works fine. There are no error messages, I can synthesize the songs, and it passes all the Check50 tests. However I can't shake this nagging ...
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1answer
27 views

Week 2 Merge Sort: Why is it assumed that the elements will be in order when they are merged?

When using the Merge Sort algorithm, I feel like everything makes sense until we start "merging" the elements back together. Why is it assumed implicitly that the process of merging will put the ...
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1answer
97 views

Enquiry on Week 2's Valid_Triangle

May I ask what does this means? How does %s derive can / cannot ? ** printf("These %s be the lengths of sides of a valid triangle.\n", valid_triangle(a, b, c) ? "can" : "cannot"); } **
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3answers
2k views

I don't understand how the collatz(n) recursive function works

If you watch the short on recursion in week2 2018, Doug explains how calculate the steps for the collatz conjecture. I don't understand how the solution he proposes can work: int collatz(int n) { ...
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1answer
68 views

Error wrapping around vigenere

so far the vigenere.c works if the keyword and the plaintext are the same size of characters, but once it tries to wrap around if the keyword is smaller than the plaintext the output goes wrong. Here ...
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1answer
53 views

expected output, but not “MB\n”

check50_more report : :) initials.c exists :) initials.c compiles :) outputs "MB" for "Milo Banana" :) outputs "MB" for "milo banana" :( outputs "MB" for " milo banana " \ expected output, but ...
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1answer
78 views

cs50 capitalize0.c from week 2 example problem

I have written the program as in the example of week 2, I can not find anything I have done differently, unfortunately. I have not declared the counting variable i and n, as in the example, however, ...
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1answer
97 views

vigenere.c done incorrectly, or check50 broken? [duplicate]

I completed vigenere.c per the spec for pset2, and it seems to be working fine. However, when I use check50, this is the result I get. So it says everything is fine, however when it checks how the ...
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1answer
117 views

Unused variable error when trying to implement the Valid_Triangle function

I am trying to implement the Valid Triangle code, however for some reason I am always getting an unused variable error for the x,y, and z variables in the main function. How do I fix? #include <...
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1answer
76 views

Can you use switch with Vigenere's?

Week 2's switch.c example really appealed to me--found it very clean and easy to read. I did Vigenere's using for loops and if statements and tried to rewrite it using a switch. My code doesn't even ...
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1answer
102 views

pset2 How to get rid of spaces in the end of the milo banana_ _ _ _ (input)?

How to get rid of spaces in the end of the input? My code works perfectly with _ _ milla_ _ _ banana But I have issues with the case if _ _ _ milla_ _ banana_ _ _ when I have spaces in the end How ...
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1answer
56 views

Problem from Section lesson “Function” but I have the following error message

When I compiled my code for the Section video titled, "Functions" where we were to make and define the function valid_triangle, the following error code was printed: triangle.c:15:9: error: expected ...
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1answer
432 views

Difference between Pass by Value and Pass by Reference (a practical example)

at the end of Doug's video on arrays he explains how variables get passed in function calls in comparison to how arrays work. void set_array(int array[4]); void set_int(int x); int main (void) { ...
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1answer
27 views

Clarification regarding for loops and arrays

In the continued lecture of week2: At about 17:00 he writes the for loop. What does i stand for? I don't think it is age, but it can't be the number of students? What does it mean? What is ages[i]? ...
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3answers
2k views

'\0' vs '0' : What's the difference?

2016 version Lecture Week 2 continued... What's the difference between \0 and 0? I have watched the lectures, but it didn't help. Thanks in advance!
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2answers
536 views

Floating Point Imprecision

In Week 2 Lecture (the first one), Mr. Malan says a reason for floating - point imprecision (40:00). I don't get his reason. Sorry for the bad question, but please explain... Thanks in advance.
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1answer
38 views

What is an Array exactly?

The short from CS50 is not giving me a clear idea about what an array is exactly. Can someone give me some more information about the array in C?
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1answer
48 views

Can anyone give me an example of code without a command-line-argument and code with a command-line-argument?

After watching the lectures, walkthrough and notes of the lectures It is still not clear to me what purpose a command-line-argument got exactly. I hope if someone can give me an example of code with ...
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1answer
51 views

2nd Week and 2nd Lecture: Dynamic array

I just took the second lesson of second week, we were taught how to do dynamic integer array, some confusions i need to clear up is when we have initialized an integer and even take the value from ...
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2answers
177 views

Why is d = 185 to satisfy de = 1 mod m (where m = 924)? (Wk2, shorts: cryptography)

At the 6:50 min mark of this video: https://courses.edx.org/courses/HarvardX/CS50x3/2015/courseware/c0986764d695405f9d995f43b7c10676/5194906ad75c4edb9ecd401df372b8f3/ here's a screen shot, too: http:/...
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2answers
33 views

Week 2 walkthroughs ages.c has a bug?

The ages.c code doesn't seem to account for a scenario where user enters a negative integer when prompted for ages. { for (int i = 0; i < n; i++) { printf("Age of ...
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0answers
46 views

Code is not working in CS50 Appliance but working in CODE BLOCKS

EVEN AFTER REPLACING #incluse with #include the code is working in code blocks but not working in cs50 appliance. Please tell me why? #include<stdio.h> #include<conio.h> main( ) { ...
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3answers
835 views

What does if (s != NULL) do?

According to the lecture in Week 2 and the walkthrough video "String", to make sure that the user gives us a valid string we use this condition: if (s != NULL) { //code } ...
1
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2answers
24 views

Why 'a'-'A', instead of 32

In the lectures and the walkthroughs for Week 2, David goes through a capitalize program. He makes a point of using the subtraction 'a'-'A' rather than simply the value 32 in order to change the case ...
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4answers
842 views

How to calculate modulo?

From the cryptography video short(Week2) , can anybody tell how to compute the value of m = c^d (mod n) ? How do we find that 658^185(mod 989) equals 67 ?