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Difference between recursion and iteration - JavaScript

Posted on 2011-09-11
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Last Modified: 2012-06-27
Hi,

Can you please provide me a simple example on:

Difference between recursion and iteration - JavaScript

Thanks
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Question by:milani_lucie
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7 Comments
 
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by:Gurvinder Pal Singh
Gurvinder Pal Singh earned 500 total points
ID: 36520714
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leakim971 earned 500 total points
ID: 36520738
Test page (recursion) : http://jsfiddle.net/Mjzkk/
function factorial_recursion(n) {
      if(n!=1) n * factorial_recursion;
}

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test page (iteration) : http://jsfiddle.net/Kvmrc/
function factorial_iteration(n) {
    a = n;
    while(n!=1) {
        n = n -1;
        a *= n;
    }
    return a;
}

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http://en.wikipedia.org/wiki/Factorial
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by:leakim971
ID: 36520739
correction (recursion) :
function factorial_recursion(n) {
    if(n!=1) n = n * factorial_recursion(n-1);
    return n;
}

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LVL 82

Expert Comment

by:leakim971
ID: 36520742
to be mathematicaly correct (and not just for the example) : 0! = 1
so :

function factorial_recursion(n) {
      if(n==0) return 1;
      if(n!=1) n * factorial_recursion(n-1);
      return n;
}

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and :
function factorial_iteration(n) {
    if(n==0) return 1;
    a = n;
    while(n!=1) {
        n = n -1;
        a *= n;
    }
    return a;
}

Open in new window

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by:sonawanekiran
sonawanekiran earned 500 total points
ID: 36520837
Recursion repeatedly invokes the mechanism itself as explained by @leakim971 using factorial number. Both iteration and recursion are based on a control structure. Iteration explicitly uses a repetition structure; recursion achieves repetition through repeated method calls.

Keep in Mind:

Recursion consequently the overhead of method calls. This can be expensive in both processor time and memory space.
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by:user_n
user_n earned 500 total points
ID: 36524822
Recursion invokes the function itself. If you do not stop the process right it might proceed forever. It takes more space in the stack of the computer (http://en.wikipedia.org/wiki/Call_stack), because of witch it usually takes more time and memory.But in some cases it is the easiest way of finding of programing solution to a problem. Some more info (http://ocw.mit.edu/courses/electrical-engineering-and-computer-science/6-046j-introduction-to-algorithms-sma-5503-fall-2005/video-lectures/)
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