90 lines
2.3 KiB
Java
90 lines
2.3 KiB
Java
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/** Author : Suraj Kumar
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* Github : https://github.com/skmodi649
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*/
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/** PROBLEM DESCRIPTION :
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* Geek created a random series and given a name geek-onacci series
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* Given four integers a, b, b, n
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* a, b, c represents the first three numbers of geek-onacci series
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* Find the Nth number of the series.
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* The nth number of geek-onacci series is a sum of the last three numbers (summation of N-1th, N-2th, and N-3th geek-onacci numbers)
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*/
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/** ALGORITHM :
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* Simply use the concept of Recursion
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* Define the base cases of the Recursion for n equal to 1 , 2 and 3
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* Then simply use recurrence in the same way as we used it in Fibonacci series
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*/
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import java.util.*;
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import java.lang.*;
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class GFG {
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public static int rec(int a,int b,int c,int n)
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{
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if(n==1)
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return a;
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else if(n==2)
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return b;
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else if(n==3)
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return c;
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else
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return rec(a,b,c,n-1)+rec(a,b,c,n-2)+rec(a,b,c,n-3);
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}
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public static void main (String[] args) {
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Scanner sc = new Scanner(System.in);
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int a,b,c,n;
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System.out.print("Enter the first number of Geek-onacci series : ");
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a = sc.nextInt();
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System.out.print("Enter the second number of Geek-onacci series : ");
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b = sc.nextInt();
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System.out.print("Enter the third number of Geek-onacci series : ");
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c = sc.nextInt();
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System.out.print("Enter the values of n : ");
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n = sc.nextInt();
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int val = rec(a,b,c,n);
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System.out.println("Nth Geek-onacci number : "+val);
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}
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}
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/** TEST CASES :
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* Test Case 1 :
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* Input : a = 1 , b = 3 , c = 2 , n = 4
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* Output : 6
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*
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* Test Case 2 :
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* Input : a = 1 , b = 3 , c = 2 , n = 5
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* Output : 11
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*
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* Test Case 3 :
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* Input : a = 1 , b = 3 , c = 2 , n = 6
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* Output : 19
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*/
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/** Explanation for a = 1 , b = 3 , c = 2 , n = 5
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* n = 5 then val = rec(1,3,2,4)+rec(1,3,2,3)+rec(1,3,2,2)
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* rec(1,3,2,2) gives 3 and rec(1,3,2,3) gives 2 hence both totally give 3 + 2 = 5
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* rec(1,3,2,4) is actually equal to rec(1,3,2,3)+rec(1,3,2,2)+rec(1,3,2,1) hence gives 2 + 3 + 1 = 6
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* Now val = 6 + 5 = 11
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* 11 will be returned as output
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*/
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/** Time Complexity : O(n)
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* Auxiliary Space Complexity : O(1)
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* Constraints : 1 <= A, B, C <= 100
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* N >= 4
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*/
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