Find First n Fibonacci Numbers (original) (raw)

Last Updated : 03 Jan, 2025

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Given an integer **n. The task is tofind the first **n Fibonacci Numbers.

**Examples :

**Input: n = 3
**Output: 0 1 1

**Input: n = 7
**Output: 0 1 1 2 3 5 8

Recursive Approach - O(n*2n) Time and O(n) Space

Find nth fibonacci number by calling for n-1 and **n-2 and adding their return value. The base case will be if n=0 or n=1 then the fibonacci number will be **0 and 1 respectively.

C++ `

#include #include using namespace std;

int findFibonacci(int n) {

// base case n = 0 n = 1 if (n == 0) { return 0; } else if (n == 1) { return 1; } else { return findFibonacci(n - 2) + findFibonacci(n - 1); } }

vector fibonacciNumbers(int n) { vector ans; for (int i = 0; i < n; i++) { ans.push_back(findFibonacci(i)); } return ans; }

int main() { int n = 7; vector res = fibonacciNumbers(n); for (int i = 0; i < res.size(); i++) { cout << res[i] << " "; } return 0; }

C

#include <stdio.h> #include <stdlib.h>

int findFibonacci(int n) { // base case n = 0 , n = 1 if (n == 0) { return 0; } else if (n == 1) { return 1; } else { return findFibonacci(n - 2) + findFibonacci(n - 1); } }

int* fibonacciNumbers(int n) { int* ans = (int*)malloc(n * sizeof(int)); for (int i = 0; i < n; i++) { ans[i] = findFibonacci(i); } return ans; }

int main() { int n = 7; int* res = fibonacciNumbers(n); for (int i = 0; i < n; i++) { printf("%d ", res[i]); } free(res); return 0; }

Java

import java.util.ArrayList; import java.util.List;

class GfG { static int findFibonacci(int n) {

  // base case n = 0 , n = 1
  if (n == 0) {
     return 0;
  } else if (n == 1) {
     return 1;
  } else {
     return findFibonacci(n - 2) + findFibonacci(n - 1);
  }

}

static List fibonacciNumbers(int n) { List ans = new ArrayList<>(); for (int i = 0; i < n; i++) { ans.add(findFibonacci(i)); } return ans; }

public static void main(String[] args) { int n = 7; List res = fibonacciNumbers(n); for (int i = 0; i < res.size(); i++) { System.out.print(res.get(i) + " "); } } }

Python

def findFibonacci(n):

#base case n = 0 , n = 1
if n == 0:
    return 0
elif n == 1:
    return 1
else:
    return findFibonacci(n-2) + findFibonacci(n-1)

def fibonacciNumbers(n): ans = [] for i in range(n): ans.append(findFibonacci(i)) return ans

if name == 'main': n = 7 res = fibonacciNumbers(n) for num in res: print(num, end=' ')

C#

using System; using System.Collections.Generic;

class GfG { static int FindFibonacci(int n) {

  // base case n = 0 , n = 1
  if (n == 0) {
     return 0;
  } else if (n == 1) {
     return 1;
  } else {
     return FindFibonacci(n - 2) + FindFibonacci(n - 1);
  }

}

static List FibonacciNumbers(int n) { List ans = new List(); for (int i = 0; i < n; i++) { ans.Add(FindFibonacci(i)); } return ans; }

static void Main() { int n = 7; List res = FibonacciNumbers(n); foreach (int num in res) { Console.Write(num + " "); } } }

JavaScript

function findFibonacci(n) {

//base case n = 0 , n = 1
if (n === 0) {
    return 0;
} else if (n === 1) {
    return 1;
} else {
    return findFibonacci(n - 2) + findFibonacci(n - 1);
}

}

function fibonacciNumbers(n) { let ans = []; for (let i = 0; i < n; i++) { ans.push(findFibonacci(i)); } return ans; }

// Driver Code let n = 7; let res = fibonacciNumbers(n); console.log(res.join(' '));

`

**Time Complexity: O(n*2n)
**Auxiliary Space: O(n), For recursion call stack.

Iterative Approach - O(n) Time and O(1) Space

To find Fibonacci numbers by maintaining two variables (f1 and f2) to represent consecutive Fibonacci numbers. Starting with 0 and 1, it iteratively computes the next Fibonacci number, appends it to the result list, and updates the variables accordingly.

C++ `

#include <bits/stdc++.h> using namespace std;

vector fibonacciNumbers(int n) { vector ans; int f1 = 0, f2 = 1, i; ans.push_back(f1);

for (i = 1; i < n; i++) { ans.push_back(f2); int next = f1 + f2; f1 = f2; f2 = next; } return ans; }

int main() { int n = 7; vector res = fibonacciNumbers(n); for (int i = 0; i < res.size(); i++) { cout << res[i] << " "; } return 0; }

Java

import java.util.ArrayList; import java.util.List;

class GfG { static List fibonacciNumbers(int n) { List ans = new ArrayList<>(); int f1 = 0, f2 = 1; ans.add(f1);

  for (int i = 1; i < n; i++) {
     ans.add(f2);
     int next = f1 + f2;
     f1 = f2;
     f2 = next;
  }
  return ans;

}

public static void main(String[] args) { int n = 7; List res = fibonacciNumbers(n); for (int num : res) { System.out.print(num + " "); } } }

Python

def fibonacci_numbers(n): ans = [] f1, f2 = 0, 1 ans.append(f1)

for i in range(1, n):
    ans.append(f2)
    next = f1 + f2
    f1 = f2
    f2 = next
return ans

if name == "main": n = 7 res = fibonacci_numbers(n) print(' '.join(map(str, res)))

C#

using System; using System.Collections.Generic;

class GfG { static List FibonacciNumbers(int n) { List ans = new List(); int f1 = 0, f2 = 1; ans.Add(f1);

  for (int i = 1; i < n; i++) {
     ans.Add(f2);
     int next = f1 + f2;
     f1 = f2;
     f2 = next;
  }
  return ans;

}

static void Main() { int n = 7; List res = FibonacciNumbers(n); foreach (int num in res) { Console.Write(num + " "); } } }

JavaScript

function fibonacciNumbers(n) { let ans = []; let f1 = 0, f2 = 1; ans.push(f1);

for (let i = 1; i < n; i++) {
    ans.push(f2);
    let next = f1 + f2;
    f1 = f2;
    f2 = next;
}
return ans;

}

// Driver Code let n = 7; let res = fibonacciNumbers(n); console.log(res.join(' '));

`

**Time Complexity: O(n)
**Auxiliary Space: O(1)