My question is, is there a general efficient algorithm to solve the generalized version of this problem for N coins with one counterfeit. Three groups of equal number of coins, weigh two of them against each other, and you'll see which of the three groups has the lower weight. Recursively apply the same algorithm to the lightest group. Note that the first 2 groups have same number of coins. Weigh the 1st group with the 2nd group. If they are unequal, then we have to find the culprit counterfeit coin from one of these groups. Podcast We chat with Kent C Dodds about why he loves React and discuss what life was like in the dark days before Git.
Learn more. Algorithm to find counterfeit coin amongst n coins Ask Question. Asked 3 years, 2 months ago. Active 2 years, 4 months ago. Viewed 2k times.
For completeness, here is one example of such a problem: A well-known example has nine or fewer items, say coins or balls , that are identical in weight save for one, which in this example is lighter than the others—a counterfeit an oddball. I'm voting to close this question as off-topic because belongs to programming. DhruvPathak Explain.
I'm asking about the specific algorithm we could use; how is that not related to stackoverflow. In China, it is completely legal to make "replica" coins from another country, and they are always achieving new and better counterfeiting techniques.
A basic skill set of how to detect counterfeit coins will hopefully save you money by avoiding the purchase of counterfeit coins. Counterfeit coins can be grouped into three different categories: struck counterfeits, cast counterfeits, and altered coins. Struck Counterfeits Counterfeiters make struck counterfeit coins the same way a mint manufactures a genuine coin by a planchet being struck between two coin dies in a coining press. The counterfeiter can create the coin dies by engraving them by hand, using the spark erosion method, using a one-to-one transfer engraving lathe, using the plating method, or the impact technique.
The counterfeiter then loads the coin dies into a coining press that uses several tons of pressure to strike the counterfeit coins. This manufacturing process is the most tedious and most expensive way of creating a counterfeit coin. Therefore, only the more valuable coins are counterfeited using the struck counterfeit method.
Cast Counterfeits An inexpensive way to produce counterfeit coins is to create a mold of the genuine coin and use it to cast a counterfeit coin.
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Creating the mold is fairly simple and straightforward. The host coin is used as a model to create the cast. Counterfeiters like this method because this process does not destroy the host coin.
Once the molds are ready, the molten metal is poured into the mold. More experienced counterfeiters will use a centrifuge to make sure that the molten metal flows to the farthest recesses of the mold.
Manvel, Counterfeit coin problems, Math. Sign up using Email and Password. Minimax and Applications pp Cite as. Finally, look carefully at the coin with a high-powered magnifying glass or stereo microscope. A false coin differs in weight from a true coin by less than 3.
Altered and Doctored Coins The cheapest and quickest way to make money by deceiving a coin collector is to take an ordinary coin and modify it to look like an expensive and rare coin. For example, a counterfeiter can purchase a Lincoln cent with the designer's initials of V. Split coins are another example of a counterfeit coin that has been radically altered. The counterfeiter will take two common coins, split them in half, and glue or solder the two halves together. This process will yield a coin that will give the illusion of a rare and more expensive coin.
Several scientific methods may give you a clue if a coin is counterfeit or not. The first is to have access to detailed specifications of a genuine coin.
These should include size, diameter, thickness, metal composition, weight, and specific gravity. Use a high precision caliper to measure the diameter and thickness of the coin. Use a scale that is accurate to within 0.
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The movie saw simultaneous screenings in Russia. It was a box office success with , tickets only from the first run in Athens, more than any other movie for that season. It has also been honored with several film awards Venice , Moscow and nominations. From Wikipedia, the free encyclopedia. This section needs expansion.