Another beginner 'n when to use while vs if

This is a discussion on Another beginner 'n when to use while vs if within the C Programming forums, part of the General Programming Boards category; I am really getting confused between using while and if loops eg: Here's a solution for swapping current element with ...

  1. #1
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    Another beginner 'n when to use while vs if

    I am really getting confused between using while and if loops

    eg: Here's a solution for swapping current element with it's left node in a binary tree:

    Code:
    TREE swap_left (TREE T){
    	element_type tmp;
    	if(T!=NULL){
    		if(T->left){
    		tmp = T->element;
    		T->element = T->left->element;
    		T->left->element = tmp;		
    		}
    
    	swap_left(T->right);
    	swap_left(T->left);
    }	
    	return T;	
    }
    why can't I replace if (T!=NULL) with while(T!=NULL)?...please give me some suggestion on when to use what....

  2. #2
    Deathray Engineer MacGyver's Avatar
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    Generally....

    Use if, if you're only needing to test the condition and run the block of code once. Use while when you need to repeatedly run the code while the condition is true until it is false.

  3. #3
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    Is this the right solution using while?

    Code:
    TREE swap_left (TREE T){
    	element_type tmp;
    	while ((T!=NULL) && (T->left!=NULL)){
    		tmp = T->element;
    		T->element = T->left->element;
    		T->left->element = tmp;	
    		return (swap_left(T->right)&&swap_left(T->left));
    		}
    	
    	return T;	
    }

  4. #4
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    I printed out the solution and it does look right....thanks for your answer Mac

  5. #5
    Woof, woof! zacs7's Avatar
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    You can't compare if with while...

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