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How to get the permutation of a number in Java
okwudili onyejiaku
Overview
A permutation is the number of ways by which we can arrange a set or an object in a definite order. The mathematical formula to calculate a permutation is given below:
Parameters
- P: This is the number of permutations.
- n: This is the number of objects.
- r: This is the number of objects selected.
We must use the above formula to get the permutation for multiple objects. We obtain the permutation by defining the factorial for n and n-r.
Here is the syntax to get the factorial using a for loop.
Syntax
for(counter; counter <= number; counter++)
{
result = result * counter;
}Syntax for finding the factorial of a number
Parameters
counter: This represents a counter. The function will use it for looping.
number: This is the input number for which we're trying to find the factorial.
Code
class HelloWorld {
// create the factorial function
public static int factorial(int num){
int result = 1, counter;
// create for loop
for(counter=1; counter<=num; counter++){
result = result*counter;
}
return result;
}
public static void main( String args[] ) {
// create some numbers of objects we want to get the combination
int n1 = 7;
int n2 = 4;
// create number of the objects are taken at a time
int r1 = 3;
int r2 = 2;
// get the permutation based on the mathematical formula
System.out.println(factorial(n1)/(factorial(r1)*factorial(n1-r1)));
System.out.println(factorial(n2)/(factorial(n2-r2)));
}
}Code to get the permutation of a number in Java
Explanation
- Line 3: We create a
factorial()function that takes an integer number and returns its factorial. - Lines 15 and 16: We create and initialize variables for the number of objects we want to get combinations of.
- Lines 19 and 20: We create and initialize the number of objects taken at a particular time for every selection.
- Lines 23 and 24: We use the mathematical formula for combinations to obtain the permutations and print the values to the console.
RELATED TAGS
java
permutation
factorial
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okwudili onyejiaku
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