67 lines
2.4 KiB
Java
67 lines
2.4 KiB
Java
// Calculating Factorial Using Big Integer
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// https://www.hackerearth.com/practice/notes/factorial-of-large-number/
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import java.math.BigInteger;
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import java.util.*;
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import java.io.*;
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import java.lang.*;
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class FactorialUsingBigInteger
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{
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//Main Method
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public static void main(String[] args) throws IOException
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{
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Scanner sc = new Scanner(System.in);
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System.out.println("Enter the number of times you want to calculate Factorial:");
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int t = sc.nextInt();
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HashMap<Integer,BigInteger> hashmap = new HashMap<>();
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int maxKey = -1;
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for(int i=0;i<t;i++){
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System.out.println("Enter the value of N:");
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int N = sc.nextInt();
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if(N>=0)
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{
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BigInteger f = new BigInteger("1"); // Or BigInteger assigned to ONE
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// Multiply f with number till N
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int initial = 2;
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//Checking if inputted number exists in map or not
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if (hashmap.containsKey(N)){
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f = hashmap.get(N);
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} else {
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// For a given number, Checking whether any sub factorial has some element present in hashmap
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if (maxKey!=-1){
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initial = maxKey;
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}
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for (int j = initial; j <= N; j++) {
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if (hashmap.containsKey(j)) {
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f = f.multiply(hashmap.get(j));
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} else {
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f = f.multiply(BigInteger.valueOf(j));
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maxKey = j;
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hashmap.put(j, f);
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}
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}
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}
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System.out.println("Factorial of given number is :"+f);
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}else{
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System.out.println("Number Should be greater than 0");
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}
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}
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}
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}
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/*
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Time Complexity:O(t*N)
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Space Complexity:O(1)
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Input:
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Enter the number of times you want to calculate Factorial:
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3
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Enter the value of N:
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20 //O(N) ==>20*19*18.....*1
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Enter the value of N:
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80 // O(N) ==>80*79*78.....*21*hashmap[20]
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Enter the value of N:
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10 // O(1) ==>hashmap[10]
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Output:
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Factorial of given number is : 2432902008176640000
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Factorial of given number is : 71569457046263802294811533723186532165584657342365752577109445058227039255480148842668944867280814080000000000000000000
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Factorial of given number is : 3628800
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*/ |