C++ Program to Find Fibonacci Numbers using Iteration

This C++ Program demonstrates the the computation of Fibonacci Numbers using Iteration.

Here is source code of the C++ Program to Find Fibonacci Numbers using Iteration. The C++ program is successfully compiled and run on a Linux system. The program output is also shown below.

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/* 
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 * C++ Program to Find Fibonacci Numbers using Iteration

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 */
```
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#include <cstring>
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#include <iostream>
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#include <cstdlib>
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#define ll long long
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using namespace std;
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```
 
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/* 
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 * Iterative function to find Fibonacci Numbers

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 */
```
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ll fibo_iter(int n)
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{
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    int previous = 1;
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    int current = 1;
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    int next = 1;
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    for (int i = 3; i <= n; ++i) 
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    {
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        next = current + previous;
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        previous = current;
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        current = next;
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    }
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    return next;
```
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}
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/* 
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 * Main
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 */
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int main()
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{
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    int n;
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    while (1)
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    {
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        cout<<"Enter the integer n to find nth fibonnaci no.(0 to exit): ";

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        cin>>n;
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        if (n == 0)
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            break;
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        cout<<fibo_iter(n)<<endl;
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    }
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    return 0;
```
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}
```

$ g++ fibo_iter.cpp
$ a.out
 
Enter the integer n to find nth fibonnaci no.(0 to exit): 1
1
Enter the integer n to find nth fibonnaci no.(0 to exit): 2
1
Enter the integer n to find nth fibonnaci no.(0 to exit): 3
2
Enter the integer n to find nth fibonnaci no.(0 to exit): 4
3
Enter the integer n to find nth fibonnaci no.(0 to exit): 5
5
Enter the integer n to find nth fibonnaci no.(0 to exit): 6
8
Enter the integer n to find nth fibonnaci no.(0 to exit): 7
13
Enter the integer n to find nth fibonnaci no.(0 to exit): 8
21
Enter the integer n to find nth fibonnaci no.(0 to exit): 9
34
Enter the integer n to find nth fibonnaci no.(0 to exit): 10
55
Enter the integer n to find nth fibonnaci no.(0 to exit): 0
 
------------------
(program exited with code: 1)
Press return to continue