I am trying to write a program in C++. It's a much longer program, but I need help regarding just one of the functions in it.
Basically, this function should get a number, and then return that same number but in ternary base. Now, my idea is to basically divide that number by 3 and collect remainders ( if my number is "n", I'd use n%3) and then I would just divide that number with 3 ( n/3 ) and go again until that number "n" by repeated division becomes 0.
This should work and convert the number to ternary base, but my problem is the fact that I do not know how to collect these remainders. This is probably a stupid question, but I am still a begginer in programming.
Basically, if I make a while loop , something like this :
while(n>0)
{
int digitofternary=n%3;
n/=3;
}
In every iteration of while loop, digitofternary is just going to change. How can I adjust this loop so digits get remembered/collected and I can return a new normal ternary base number from function?
Sorry if this sounded confusing, hope it didn't ( I am not a native english speaker ).
int sample_fn (int n)
{
std::string str_ret;
while(n>0)
{
int digitofternary=n%3;
n/=3;
std::string str= std::to_string(digitofternary);
str_ret.append(str);
}
return std::stoi(str_ret);
}
Related
This question already has answers here:
Why does division result in zero instead of a decimal?
(5 answers)
Closed 1 year ago.
I am having some trouble and I cant really even figure out what is wrong, so I needed some help.
I need to take a percentage of a number that one of the structs in my array has, for each one.
my struct looks like
struct person{
int number;
string name;
float share;
}
So I use a for loop to get the total of number, no problem, all comes out good. But when I try to get what percent of the total I always get a zero.
for (int i=0; i<numberOfPersons;i++){
people[i].share = 100 * ((people[i].number)/totalNumber);
}
I don't understand what is going wrong here but people[i].share always comes out as 0.00 when I cout it.
literally all I do after this is cout it and I get the correct values from number and totalNumber. So I'm like really confused.
If I flip the division problem around I get answers(not the right ones obviously), so I know that there is data in the fields when the for loop runs. But where is it going when I run the equation the way I need to run it?
I tried initializing it and leaving uninitialized, swapping the pointers for ints made inside the loop, and more and I always get the same result.
Please help me understand.
I presume your type of totalnumber is int and person.number is int as well.
For operation between ints, the return value is still int
Expanding people[i].share = 100 * ((people[i].number)/totalNumber);
It would be something like people[i].share = 100 * ( 1/10 );
=> people[i].share = 100 * ( 0 );
=> people[i].share = 0;
So you will get 0 as a result;
To prevent it, cast one of int to float.
people[i].share = 100 * ((static_cast<float>(people[i].number))/totalNumber);
I'm currently trying to design an algorithm that doing such thing:
I got two strings A and B which consist of lowercase characters 'a'-'z'
and I can modify string A using the following operations:
1. Select two characters 'c1' and 'c2' from the character set ['a'-'z'].
2. Replace all characters 'c1' in string A with character 'c2'.
I need to find the minimum number of operations needed to convert string A to string B when possible.
I have 2 ideas that didn't work
1. Simple range-based for cycle that changes string B and compares it with A.
2. Idea with map<char, int> that does the same.
Right now I'm stuck on unit-testing with such situation : 'ab' is transferable to 'ba' in 3 iterations and 'abc' to 'bca' in 4 iterations.
My algorithm is wrong and I need some fresh ideas or working solution.
Can anyone help with this?
Here is some code that shows minimal RepEx:
int Transform(string& A, string& B)
{
int count = 0;
if(A.size() != B.size()){
return -1;
}
for(int i = A.size() - 1; i >= 0; i--){
if(A[i]!=B[i]){
char rep_elem = A[i];
++count;
replace(A.begin(),A.end(),rep_elem,B[i]);
}
}
if(A != B){
return -1;
}
return count;
}
How can I improve this or I should find another ideas?
First of all, don't worry about string operations. Your problem is algorithmic, not textual. You should somehow analyze your data, and only afterwards print your solution.
Start with building a data structure which tells, for each letter, which letter it should be replaced with. Use an array (or std::map<char, char> — it should conceptually be similar, but have different syntax).
If you discover that you should convert a letter to two different letters — error, conversion impossible. Otherwise, count the number of non-trivial cycles in the conversion graph.
The length of your solution will be the number of letters which shouldn't be replaced by themselves plus the number of cycles.
I think the code to implement this would be too long to be helpful.
I am trying to find the sum of each digit in an integer squared, and for any integer that is input to sqdnumber, it outputs 0 to sqdNumber_result, and I can't figure out why.
Also, this is through edX, but I have been stuck for a week or so on this problem, and I have looked at a lot of different topics, but haven't found anything of use to me.
I used codeblocks to write this, but the system testing it uses codeboard
void squaredSum(int sqdnumber,int &sqdNumber_result) {
for (int i=1; i>1; i++){
if (sqdnumber >= ((10^(i-1))-1)){
int rem = (sqdnumber % (10^i));
int rem1 = (sqdnumber % (10^(i-1)));
int temp = (rem - rem1);
sqdNumber_result = sqdNumber_result + (temp^2);
}
else{
break;
}
}
}
I am new to coding, and just learning to do loops in C++.
This is the first iteration of the loop I have gotten their system to actually give me an output for it(I've written and rewritten it 20 or so times), but it isn't giving me an output that makes sense.
I wouldn't ask but I am at my wit's end.
In C++, ^ is the xor operator, not the nth power. for that, you should use pow.
The for statement does not loop. The condition is false the first iteration
There are two issues:
for (int i=1; i>1; i++){
This loop will not loop at all, since the condition i>1 is never met.
The second issue is the usage of ^ to do a power operation. The ^ in C++ is not a power operator, it is the exclusive-or operator.
So the answer at first glance would be to use the std::pow function to compute powers. However there can be drawbacks using it if the exponent is an integer. The reason is that pow is not guaranteed to work perfectly for integer powers.
See this as to dangers of using pow() for integral exponents
It is advised to just use a simple array of values with the powers of 10 and doing a lookup.
you said you were new to C++ so I tried to get a solution without using the for loop and tried to make it as simple as I could.
Let me know if this was any help.
//Code to calculate the sum of each digit squared//
#include<iostream>
using namespace std;
int main ()
{
int integer1,integer2,sum, square;
cout<<"Please enter two integers"<<endl;
cin>>integer1>>integer2 ;
cout<<"The sum of your integers is"<<" "<<endl;
sum = (integer1+integer2);
cout<<sum<<endl;
cout<<"The square of your sum is"<<" "<<endl;
square = (sum*sum);
cout<<square<<endl;
return 0;
}
I have an array of letters of an unknown number of elements which contains lower case letters. I have written a function for converting a lower case number to its ASCII value
int returnVal (char x)
{
return (int) x;
}
I am trying to combine all of these values into one number. Subtracting 87 from each of these means that the value is always a 2 digit number. I am able to combine an array made up if two elements by:
returnVal (foo[0]) - 87) + returnVal (foo[1] - 87) * 100
an array made up of three elements by
returnVal (foo[0]) - 87) + returnVal (foo[1] -87) * 100 + returnVal (foo[2] - 87) * 100 * 100
I am multiplying each element by 100^its position in the array and summing them. This means that [a,b,c] would become 121110 (yes, the 'flip' having the value for 'c' first and 'a' last is intentional). Could anybody programme this (for an array of an unknown number of elements)?
EDIT: I have received no form of schooling at programming/computer science at any pojnt in my life, this is not homework. I am trying to teach myself and I have got stuck; I don't know anybody in person who I could go to for help so I asked here, apologies to those of you who are offended.
EDIT2: I know that this opinion is going to annoy a lot of people; what is the purpose of stackoverflow.com if it is not to exchange information? If I were a child who was stuck with my homework (I'm not) surely that is a valid reason for using stack overflow? Many people on this website seem to have the mindset that if a problem is asked by a beginner then it is not worth answering, which is completely fine because your time is your own. However, what genuinely bugs me is the people who see a question which they deem trivial and say "homework" and vote it down immediately. I think that this website would be far better if there wasn't an "minimum-level" knowledge required in order to ask questions, the "elitist" mindset is just childish in my opinion.
Since this is a learning exercise, here are some hints for you to complete the task yourself:
Prepare a value that will server as the "running total" for your number so far.
Start the running total at zero.
When you convert a number, say, "1234", to an int, this value would first become 1, then 12, then 123, and finally 1234
The final value of the running total is your end result
To go from a previous value to the next, multiply the prior value by ten, and add the value of the current digit to it
Your returnVal does not make sense, because in C you can very often avoid an explicit conversion of char to int. You can definitely avoid it in this case.
Making a function int digit(char c) that returns a value of decimal digit, i.e. c-'a', would be a lot more useful, because it would let you get rid of your c-87 in multiple spots.
char array[SIZE];
long factor=1;
long result=0;
for(int i=0; i<SIZE; i++)
{
result+=returnVal(foo[i])-87)*factor;
factor*=100;
}
This should work for as long as long is large enough to hold the value of 100^the position and, of course, as long as the result does not overflow.
In generating the 'check digit' in Luhn's algorithm
The check digit (x) is obtained by computing the sum of digits then computing 9 times that value modulo 10 (in equation form, (67 * 9
mod 10)). In algorithm form: Compute the sum of the digits (67).
Multiply by 9 (603). The last digit, 3, is the check digit.
Natural instincts point towards taking an id as a string to make individual digit operation easier. But there seems to be no way to extract a digit at a time through stringstream since there's no delimiter(as far as I can tell). So the process turns into a cumbersome conversion of individual characters to ints...
There's modulus for each digit approach as well, which also takes a bit of work.
I guess what I'm getting at is that I feel maybe I'm overlooking a more elegant way taking an input and operating on the input as if they were single digit inputs.
Use modular arithmetic to simply the equation like following :-
checkdigit = (sum_digits*9)%10
= ((sum_digits)%10*9)%10
Now sum_digits%10 is very simple to evaluate using strings.
C++ implementation :-
#include<iostream>
using namespace std;
int main() {
char* str = new char[100];
cout<<"Enter the String: ";
cin>>str;
int val = 0;
for(int i=0;str[i]!=0;i++) {
val = (val+str[i]-'0')%10;
}
val = (val*9)%10;
cout<<"Checkdigit("<<str<<") = "<<val;
return 0;
}
Stringstream has to calculate all digits and then convert each digit to a char by adding '0'. You'd have to subtract '0' again to get the digit values back. You'd be better off using the modulo approach directly.