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Added getFactors and getPrimes functions

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Mattrixwv
2020-08-23 04:32:55 -04:00
parent 9bf912fd89
commit b52c6bc23d
1 changed files with 227 additions and 0 deletions
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227
CSClasses/Algorithms.cs
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@@ -95,5 +95,232 @@ namespace mee{
fibNums.RemoveAt(fibNums.Count - 1); fibNums.RemoveAt(fibNums.Count - 1);
return fibNums; return fibNums;
} }
//These functions return all factors of goalNumber
public static List<int> getFactors(int goalNumber){
//You need to get all the primes that could be factors of this number so you can test them
int topPossiblePrime = (int)Math.Ceiling(Math.Sqrt(goalNumber));
List<int> primes = getPrimes(topPossiblePrime);
List<int> factors = new List<int>();
//YOu need to step through each prime and see if it is a factor in the number
for(int cnt = 0;cnt < primes.Count;){
//If the prime is a factor you need to add it to the factor list
if((goalNumber % primes[cnt]) == 0){
factors.Add(primes[cnt]);
goalNumber /= primes[cnt];
}
//Otherwise advance the location in primes you are looking at
//By noit advancing if the prime is a factor you allow for multiple of the same prime as a factor
else{
++cnt;
}
}
//If you didn't get any factors the number itself must be a prime
if(factors.Count == 0){
factors.Add(goalNumber);
goalNumber /= goalNumber;
}
//TODO: If for some reason the goalNumber is not 1 throw an error
//Return the list of factors
return factors;
}
public static List<long> getFactors(long goalNumber){
//You need to get all the primes that could be factors of this number so you can test them
long topPossiblePrime = (long)Math.Ceiling(Math.Sqrt(goalNumber));
List<long> primes = getPrimes(topPossiblePrime);
List<long> factors = new List<long>();
//YOu need to step through each prime and see if it is a factor in the number
for(int cnt = 0;cnt < primes.Count;){
//If the prime is a factor you need to add it to the factor list
if((goalNumber % primes[cnt]) == 0){
factors.Add(primes[cnt]);
goalNumber /= primes[cnt];
}
//Otherwise advance the location in primes you are looking at
//By noit advancing if the prime is a factor you allow for multiple of the same prime as a factor
else{
++cnt;
}
}
//If you didn't get any factors the number itself must be a prime
if(factors.Count == 0){
factors.Add(goalNumber);
goalNumber /= goalNumber;
}
//TODO: If for some reason the goalNumber is not 1 throw an error
//Return the list of factors
return factors;
}
public static List<BigInteger> getFactors(BigInteger goalNumber){
//You need to get all the primes that could be factors of this number so you can test them
BigInteger topPossiblePrime = (BigInteger)Math.Exp(BigInteger.Log(goalNumber) / 2);
List<BigInteger> primes = getPrimes(topPossiblePrime);
List<BigInteger> factors = new List<BigInteger>();
//YOu need to step through each prime and see if it is a factor in the number
for(int cnt = 0;cnt < primes.Count;){
//If the prime is a factor you need to add it to the factor list
if((goalNumber % primes[cnt]) == 0){
factors.Add(primes[cnt]);
goalNumber /= primes[cnt];
}
//Otherwise advance the location in primes you are looking at
//By noit advancing if the prime is a factor you allow for multiple of the same prime as a factor
else{
++cnt;
}
}
//If you didn't get any factors the number itself must be a prime
if(factors.Count == 0){
factors.Add(goalNumber);
goalNumber /= goalNumber;
}
//TODO: If for some reason the goalNumber is not 1 throw an error
//Return the list of factors
return factors;
}
//These functions return a list with all the prime number <= goalNumber
public static List<int> getPrimes(int goalNumber){
List<int> primes = new List<int>(); //Holds the prime numbers
bool foundFactor = false; //A flag for whether a factor of the current number has been found
//If the number is 0 or negative return an empty list
if(goalNumber <= 1){
return primes;
}
//Otherwise the number is at least 2, so 2 should be added to the list
else{
primes.Add(2);
}
//We can now start at 3 and skip all even numbers, because they cannot be prime
for(int possiblePrime = 3;possiblePrime <= goalNumber;possiblePrime += 2){
//Check all current primes, up to sqrt(possiblePrime), to see if there is a divisor
int topPossibleFactor = (int)Math.Ceiling(Math.Sqrt(possiblePrime));
//We can safely assume that there will be at least 1 element in the primes list because of 2 being added before this
for(int primesCnt = 0;primes[primesCnt] <= topPossibleFactor;){
if((possiblePrime % primes[primesCnt]) == 0){
foundFactor = true;
break;
}
else{
++primesCnt;
}
//Check if the index has gone out of range
if(primesCnt >= primes.Count){
break;
}
}
//If you didn't find a factor then the current number must be prime
if(!foundFactor){
primes.Add(possiblePrime);
}
else{
foundFactor = false;
}
}
//Sort the list before returning it
primes.Sort();
return primes;
}
public static List<long> getPrimes(long goalNumber){
List<long> primes = new List<long>(); //Holds the prime numbers
bool foundFactor = false; //A flag for whether a factor of the current number has been found
//If the number is 0 or negative return an empty list
if(goalNumber <= 1){
return primes;
}
//Otherwise the number is at least 2, so 2 should be added to the list
else{
primes.Add(2);
}
//We can now start at 3 and skip all even numbers, because they cannot be prime
for(long possiblePrime = 3;possiblePrime <= goalNumber;possiblePrime += 2){
//Check all current primes, up to sqrt(possiblePrime), to see if there is a divisor
long topPossibleFactor = (long)Math.Ceiling(Math.Sqrt(possiblePrime));
//We can safely assume that there will be at least 1 element in the primes list because of 2 being added before this
for(int primesCnt = 0;primes[primesCnt] <= topPossibleFactor;){
if((possiblePrime % primes[primesCnt]) == 0){
foundFactor = true;
break;
}
else{
++primesCnt;
}
//Check if the index has gone out of range
if(primesCnt >= primes.Count){
break;
}
}
//If you didn't find a factor then the current number must be prime
if(!foundFactor){
primes.Add(possiblePrime);
}
else{
foundFactor = false;
}
}
//Sort the list before returning it
primes.Sort();
return primes;
}
public static List<BigInteger> getPrimes(BigInteger goalNumber){
List<BigInteger> primes = new List<BigInteger>(); //Holds the prime numbers
bool foundFactor = false; //A flag for whether a factor of the current number has been found
//If the number is 0 or negative return an empty list
if(goalNumber <= 1){
return primes;
}
//Otherwise the number is at least 2, so 2 should be added to the list
else{
primes.Add(2);
}
//We can now start at 3 and skip all even numbers, because they cannot be prime
for(BigInteger possiblePrime = 3;possiblePrime <= goalNumber;possiblePrime += 2){
//Check all current primes, up to sqrt(possiblePrime), to see if there is a divisor
BigInteger topPossibleFactor = (BigInteger)Math.Exp(BigInteger.Log(possiblePrime) / 2);
//We can safely assume that there will be at least 1 element in the primes list because of 2 being added before this
for(int primesCnt = 0;primes[primesCnt] <= topPossibleFactor;){
if((possiblePrime % primes[primesCnt]) == 0){
foundFactor = true;
break;
}
else{
++primesCnt;
}
//Check if the index has gone out of range
if(primesCnt >= primes.Count){
break;
}
}
//If you didn't find a factor then the current number must be prime
if(!foundFactor){
primes.Add(possiblePrime);
}
else{
foundFactor = false;
}
}
//Sort the list before returning it
primes.Sort();
return primes;
}
} }
} }