Lucas Number | Practice | GeeksforGeeks

Handle	Score
@Ibrahim Nash	6379
@blackshadows	6329
@mb1973	5358
@Quandray	5231
@akhayrutdinov	5111
@saiujwal13083	4510
@sanjay05	3762
@marius_valentin_dragoi	3522
@sushant_a	3459
@verma_ji	3357
@KshamaGupta	3318
Complete Leaderboard
Handle	Score
@ritiksethi21	1050
@aroranayan999	807
@RizulBansal	685
@ashishtrehan002	538
@hemantgarg923	528
@simrangoyal	526
@ronaldo77	520
@anishrajan	505
@thanosagain	505
@ssparteek470	495
@rahul2312	491
Complete Leaderboard

Handle

Score

6379

6329

5358

5231

5111

4510

3762

@marius_valentin_dragoi

3522

@sushant_a

3459

@verma_ji

3357

@KshamaGupta

3318

Complete Leaderboard

Lucas Number

Easy Accuracy: 35.38% Submissions: 99 Points: 2

A Lucas Number is a number which is represented by the following recurrence
L_n = L_n-1 + L_n-2 for n>1
L₀ = 2
L₁ = 1

Given a number N, find the N^th lucas number.

Note: Since the output may be very large calculate the answer modulus 10^9+7.

Example 1:

Input:
N = 5
Output: 11
Explanation: L₃ + L₄ = L₅L₃= 4 and L₄ = 7

â€‹Example 2:

Input: 
N = 7
Output: 29
Explanation: L₅ + L₆ = L₇
L₅= 11 and L₆ = 18

Your Task:
You don't need to read input or print anything. Your task is to complete the function lucas() which takes integer N as input parameter and return N^th Lucas number.

Expected Time Complexity: O(N)
Expected Auxiliary Space: O(1)

Constraints:
1 <= N <= 10⁶

Topic Tags

Dynamic Programming Series

to report an issue on this page.

Editorial

We strongly recommend solving this problem on your own before viewing its editorial. Do you still want to view the editorial?

Yes

All Submissions

My Submissions:

Lucas Number

Loading...

Editorial

All Submissions

My Submissions:

Output Window

Message

Loading...

Editorial

All Submissions

My Submissions:

Output Window

Select Operation Mode