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‫In this video, we're going to do an introduction of depth first search preorder.

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‫And after we do pre-order, we're also going to do post order and in order.

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‫So I'm going to bring up a tree and with pre order we're going to start at the root and we're going

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‫to output the value 47 and we're always going to go to the left first.

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‫So we'll go left and output 21 and then we'll go to the left again and output the 18.

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‫Now the 18 is going to try to go left, but there's not a node there.

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‫Then it will try to go right and there's not a node there either.

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‫So we're done with the 18 and then we come back up to the 21.

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‫It has already gone left.

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‫Now it's going to go right to the 27 and the 27 is going to look left and look right.

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‫And then we come back up to the 21 and then we're going to go all the way back up to the 47.

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‫It has already gone left.

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‫Now it's going to go right to the 76.

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‫And as I mentioned, we're always going to go left first.

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‫So we're going to go to the 52 now.

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‫We're going to come back up to the 76, which has already gone left.

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‫Now it's going to go right and print out the 82.

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‫So this will also be our first tree traversal function to use recursion.

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‫But for now that is our introduction to depth.

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‫First Search Preorder.