# Nearest Fibonacci Number to N

Given a positive integer **N**, the task is to find the nearest Fibonacci number to the given integer **N**. If there are two Fibonacci Numbers having same difference from **N**, then print the smaller value.

**Examples:**

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Input:N = 20Output:21Explanation:Nearest Fibonacci number to 20 is 21.

Input:N = 17Output:13

**Approach:** Follow the steps below to solve the problem:

- If
**N**is equal to**0**, then print**0**as the result. - Initialize a variable, say
**ans**, to store the Fibonacci Number nearest to**N**. - Initialize two variables, say
**First**as**0**, and**Second**as**1**, to store the first and second terms of the Fibonacci Series. - Store the sum of
**First**and**Second**in a variable, say**Third**. - Iterate until the value of
**Third**is at most**N**and perform the following steps:- Update the value of
**First**to**Second**and**Second**to**Third**. - Store the sum of
**First**and**Second**in the variable**Third**.

- Update the value of
- If the absolute difference of
**Second**and**N**is at most the value of**Third**and**N**, then update the value of**ans**as**Second**. - Otherwise, update the value of
**ans**as**Third**. - After completing the above steps, print the value of
**ans**as the result.

Below is the implementation of the above approach:

## C++

`// C++ program for the above approach` `#include <bits/stdc++.h>` `using` `namespace` `std;` `// Function to find the Fibonacci` `// number which is nearest to N` `void` `nearestFibonacci(` `int` `num)` `{` ` ` `// Base Case` ` ` `if` `(num == 0) {` ` ` `cout << 0;` ` ` `return` `;` ` ` `}` ` ` `// Initialize the first & second` ` ` `// terms of the Fibonacci series` ` ` `int` `first = 0, second = 1;` ` ` `// Store the third term` ` ` `int` `third = first + second;` ` ` `// Iterate until the third term` ` ` `// is less than or equal to num` ` ` `while` `(third <= num) {` ` ` `// Update the first` ` ` `first = second;` ` ` `// Update the second` ` ` `second = third;` ` ` `// Update the third` ` ` `third = first + second;` ` ` `}` ` ` `// Store the Fibonacci number` ` ` `// having smaller difference with N` ` ` `int` `ans = (` `abs` `(third - num)` ` ` `>= ` `abs` `(second - num))` ` ` `? second` ` ` `: third;` ` ` `// Print the result` ` ` `cout << ans;` `}` `// Driver Code` `int` `main()` `{` ` ` `int` `N = 17;` ` ` `nearestFibonacci(N);` ` ` `return` `0;` `}` |

## Java

`// Java program for the above approach` `class` `GFG{` ` ` `// Function to find the Fibonacci` `// number which is nearest to N` `static` `void` `nearestFibonacci(` `int` `num)` `{` ` ` ` ` `// Base Case` ` ` `if` `(num == ` `0` `)` ` ` `{` ` ` `System.out.print(` `0` `);` ` ` `return` `;` ` ` `}` ` ` `// Initialize the first & second` ` ` `// terms of the Fibonacci series` ` ` `int` `first = ` `0` `, second = ` `1` `;` ` ` `// Store the third term` ` ` `int` `third = first + second;` ` ` `// Iterate until the third term` ` ` `// is less than or equal to num` ` ` `while` `(third <= num)` ` ` `{` ` ` ` ` `// Update the first` ` ` `first = second;` ` ` `// Update the second` ` ` `second = third;` ` ` `// Update the third` ` ` `third = first + second;` ` ` `}` ` ` `// Store the Fibonacci number` ` ` `// having smaller difference with N` ` ` `int` `ans = (Math.abs(third - num) >=` ` ` `Math.abs(second - num)) ?` ` ` `second : third;` ` ` `// Print the result` ` ` `System.out.print(ans);` `}` `// Driver Code` `public` `static` `void` `main (String[] args)` `{` ` ` `int` `N = ` `17` `;` ` ` ` ` `nearestFibonacci(N);` `}` `}` `// This code is contributed by AnkThon` |

## Python3

`# Python3 program for the above approach` `# Function to find the Fibonacci` `# number which is nearest to N` `def` `nearestFibonacci(num):` ` ` ` ` `# Base Case` ` ` `if` `(num ` `=` `=` `0` `):` ` ` `print` `(` `0` `)` ` ` `return` ` ` `# Initialize the first & second` ` ` `# terms of the Fibonacci series` ` ` `first ` `=` `0` ` ` `second ` `=` `1` ` ` `# Store the third term` ` ` `third ` `=` `first ` `+` `second` ` ` `# Iterate until the third term` ` ` `# is less than or equal to num` ` ` `while` `(third <` `=` `num):` ` ` ` ` `# Update the first` ` ` `first ` `=` `second` ` ` `# Update the second` ` ` `second ` `=` `third` ` ` `# Update the third` ` ` `third ` `=` `first ` `+` `second` ` ` `# Store the Fibonacci number` ` ` `# having smaller difference with N` ` ` `if` `(` `abs` `(third ` `-` `num) >` `=` ` ` `abs` `(second ` `-` `num)):` ` ` `ans ` `=` `second` ` ` `else` `:` ` ` `ans ` `=` `third` ` ` `# Print the result` ` ` `print` `(ans)` `# Driver Code` `if` `__name__ ` `=` `=` `'__main__'` `:` ` ` ` ` `N ` `=` `17` ` ` ` ` `nearestFibonacci(N)` `# This code is contributed by SURENDRA_GANGWAR` |

## C#

`// C# program for the above approach` `using` `System;` `class` `GFG{` `// Function to find the Fibonacci` `// number which is nearest to N` `static` `void` `nearestFibonacci(` `int` `num)` `{` ` ` ` ` `// Base Case` ` ` `if` `(num == 0)` ` ` `{` ` ` `Console.Write(0);` ` ` `return` `;` ` ` `}` ` ` `// Initialize the first & second` ` ` `// terms of the Fibonacci series` ` ` `int` `first = 0, second = 1;` ` ` `// Store the third term` ` ` `int` `third = first + second;` ` ` `// Iterate until the third term` ` ` `// is less than or equal to num` ` ` `while` `(third <= num)` ` ` `{` ` ` ` ` `// Update the first` ` ` `first = second;` ` ` `// Update the second` ` ` `second = third;` ` ` `// Update the third` ` ` `third = first + second;` ` ` `}` ` ` `// Store the Fibonacci number` ` ` `// having smaller difference with N` ` ` `int` `ans = (Math.Abs(third - num) >=` ` ` `Math.Abs(second - num)) ?` ` ` `second : third;` ` ` `// Print the result` ` ` `Console.Write(ans);` `}` `// Driver Code` `public` `static` `void` `Main(` `string` `[] args)` `{` ` ` `int` `N = 17;` ` ` ` ` `nearestFibonacci(N);` `}` `}` `// This code is contributed by sanjoy_62` |

## Javascript

`<script>` `// Javascript program for the above approach` `// Function to find the Fibonacci` `// number which is nearest to N` `function` `nearestFibonacci(num)` `{` ` ` `// Base Case` ` ` `if` `(num == 0) {` ` ` `document.write(0);` ` ` `return` `;` ` ` `}` ` ` `// Initialize the first & second` ` ` `// terms of the Fibonacci series` ` ` `let first = 0, second = 1;` ` ` `// Store the third term` ` ` `let third = first + second;` ` ` `// Iterate until the third term` ` ` `// is less than or equal to num` ` ` `while` `(third <= num) {` ` ` `// Update the first` ` ` `first = second;` ` ` `// Update the second` ` ` `second = third;` ` ` `// Update the third` ` ` `third = first + second;` ` ` `}` ` ` `// Store the Fibonacci number` ` ` `// having smaller difference with N` ` ` `let ans = (Math.abs(third - num)` ` ` `>= Math.abs(second - num))` ` ` `? second` ` ` `: third;` ` ` `// Print the result` ` ` `document.write(ans);` `}` `// Driver Code` ` ` `let N = 17;` ` ` `nearestFibonacci(N);` `// This code is contributed by subhammahato348.` `</script>` |

**Output:**

13

**Time Complexity:** O(log N)**Auxiliary Space:** O(1)