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Showing content from https://www.geeksforgeeks.org/dsa/program-to-print-first-n-fibonacci-numbers/ below:

Find First n Fibonacci Numbers

Last Updated : 03 Jan, 2025

Try it on GfG Practice

Given an integer n. The task is to find 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 n^th 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 <iostream>
#include <vector>
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<int> fibonacciNumbers(int n) {
   vector<int> ans;
   for (int i = 0; i < n; i++) {
      ans.push_back(findFibonacci(i));
   }
   return ans;
}

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


 #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<Integer> fibonacciNumbers(int n) {
      List<Integer> 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<Integer> 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=' ')


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

   static void Main() {
      int n = 7;
      List<int> 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<int> fibonacciNumbers(int n) {
   vector<int> 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<int> 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<Integer> fibonacciNumbers(int n) {
      List<Integer> 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<Integer> 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)))


 using System;
using System.Collections.Generic;

class GfG {
   static List<int> FibonacciNumbers(int n) {
      List<int> ans = new List<int>();
      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<int> 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)

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