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POusing backtracking with tree
 

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  1. POusing backtracking with tree
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    <p>I'm using the backtracking algorithm in tree thanks to a stack (with push and pop). It works but i've got a problem. The path given by the stack is "wrong".</p> <pre><code>bool Prefix(Node*root, stack *tas, char *search) { if (!isEmpty(root)) { if (strcmp(search,root-&gt;data) != 0) push(tas, root-&gt;data, search, root); if (strcmp(search,root-&gt;data) == 0) { return True ; } Prefix(root-&gt;left, tas, search); Prefix(root-&gt;right, tas, search); } return False; } </code></pre> <p>For example, i've got a tree as :</p> <pre><code> Root / \ A B / \ / \ C D E F </code></pre> <p>When I want the path of C for example, this function returns R A B (ok for R and A, not B).</p> <p>I don't know if it comes from this function or the push() function. If you don't see any error in the function, I will paste push() but it's quite long.</p> <p>Edit: I better understand now, I've added to the function :<br> if node is a leaf, pop(). If I search F, it returns me R A B F instead of R B F. I don't konw how to avoid to keep A in the stack.</p> <p>edit2 :</p> <p>Here is the code : (returns R A B F instead of R B F)</p> <pre><code>bool Prefix(Node*root, stack *tas, char *search) { if (!isEmpty(root)) { if (strcmp(search,root-&gt;data) == 0) return True ; if (LeafOrNot(root) == True ){ //it's a leaf, pop() pop(tas); if (Prefix(root-&gt;left, tas, search)) return True; if (Prefix(root-&gt;right, tas, search)) return True; } return False; } </code></pre> <p>I don't understand how I can pop traversing child node to obtain the good result, maybe adding a else to if (Prefix(root->left, tas, search)) ? Anyone have an idea ?</p> <p>thanks !</p>
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    1. COYou're almost there. If you pop from the stack not just at the leaf node but after traversing any child nodes, this will give you the result you want. Just be sure that you don't pop off the stack when the node is found. If you're searching for D, it will be push Root, push A, push C, pop C, push D, found... unwind all the way back up the call chain. If you're searching for F: push Root, push A, push C, pop C, push D, pop D, pop A, push B, push E, pop E, push F, found, unwind... Hope this helps.
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    2. COI've tried to had another pop(tas) but it doesn't work. I need to change the code's structure ? thanks
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