Algorithmic inference: Difference between revisions
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The '''change-making problem''' addresses the following question: how can a given amount of money be made with the least number of coins of given denominations? It is a [[knapsack problem| knapsack type problem]], and has applications wider than just currency. | |||
==Mathematical definition== | |||
Given a set of integer coin values {''w''<sub>1</sub>, ''w''<sub>2</sub>, ..., ''w''<sub>''n''</sub>} where ''w''<sub>1</sub> = 1 and ''w''<sub>''j''</sub> < ''w''<sub>''j''+1</sub> for 1 ≤ ''j'' ≤ ''n'' − 1, and a positive integer ''W'', find a set of non-negative integers {''x''<sub>1</sub>, ''x''<sub>2</sub>, ..., ''x''<sub>''n''</sub>} which minimize | |||
: <math>\sum_{j=1}^n x_j</math> | |||
subject to | |||
: <math>\sum_{j=1}^n w_j x_j = W.</math> | |||
==Non currency examples== | |||
An application of change-making problem can be found in computing the ways one can make a [[nine dart finish]] in a game of darts. | |||
==Methods of solving== | |||
===Dynamic programming=== | |||
Making a list of ways to make each amount from one upwards (an example of a [[dynamic programming]] method) | |||
===Linear programming=== | |||
[[Linear_programming#Integer_unknowns | Integer Linear Programming]] is often a quick way to solve this kind of problem, but the time it will take to resolve the problem is not certain, and may be slow in some cases | |||
===Greedy method=== | |||
In the US (and most other) coin systems, a [[greedy algorithm]] of picking the largest denomination of coin which is not greater than the remaining amount to be made will always produce the optimal result. This is not automatically the case, though: if the coin denominations were 1, 3 and 4, then to make 6, the greedy algorithm would choose three coins (4,1,1) whereas the optimal solution is two coins (3,3). | |||
== Related problems == | |||
The "optimal [[denomination (currency) | denomination]] problem"<ref> | |||
{{cite journal |author=J. Shallit |title=What this country needs is an 18c piece |journal=[[Mathematical Intelligencer]] |volume=25 |issue=2 |pages=20–23 |doi=10.1007/BF02984830 |url=http://www.cs.uwaterloo.ca/~shallit/Papers/change2.pdf}} | |||
</ref> | |||
is a problem for people who design entirely new currencies: | |||
What denominations should be chosen for the coins | |||
in order to minimize the average cost of making change -- | |||
i.e., the average number of coins needed to make change? | |||
The version of this problem assumed that the people making change will use the minimum number of coins | |||
(from the denominations available). | |||
One variation of this problem assumes that the people making change will use the "greedy algorithm" for making change, even when that requires more than the minimum number of coins. | |||
Most current currencies use a [[1-2-5 series]], | |||
but some other set of denominations would require fewer denominations of coins or a smaller average number of coins to make change or both. | |||
==See also== | |||
* [[List of knapsack problems]] | |||
* [[Coin problem]] | |||
* [[package-merge algorithm#The coin collector's problem | The coin collector's problem]] | |||
==References== | |||
{{reflist}} | |||
* {{cite journal |author=X. Cai |title=Canonical Coin Systems for Change-Making Problems |journal=Proceedings of the Ninth International Conference on Hybrid Intelligent Systems |year=2009 |pages=499–504 |doi=10.1109/HIS.2009.103 |arxiv=0809.0400}} | |||
* {{cite journal |author=M. Adamaszek, A. Niewiarowska |title=Combinatorics of the change-making problem |journal=European Journal of Combinatorics |volume=31 |issue=1 |year=2010 |pages=47–63 |doi=10.1016/j.ejc.2009.05.002 |arxiv=0801.0120}} | |||
[[Category:Number theory]] | |||
[[Category:Recreational mathematics]] | |||
[[Category:Combinatorial optimization]] |
Revision as of 09:01, 19 December 2013
The change-making problem addresses the following question: how can a given amount of money be made with the least number of coins of given denominations? It is a knapsack type problem, and has applications wider than just currency.
Mathematical definition
Given a set of integer coin values {w1, w2, ..., wn} where w1 = 1 and wj < wj+1 for 1 ≤ j ≤ n − 1, and a positive integer W, find a set of non-negative integers {x1, x2, ..., xn} which minimize
subject to
Non currency examples
An application of change-making problem can be found in computing the ways one can make a nine dart finish in a game of darts.
Methods of solving
Dynamic programming
Making a list of ways to make each amount from one upwards (an example of a dynamic programming method)
Linear programming
Integer Linear Programming is often a quick way to solve this kind of problem, but the time it will take to resolve the problem is not certain, and may be slow in some cases
Greedy method
In the US (and most other) coin systems, a greedy algorithm of picking the largest denomination of coin which is not greater than the remaining amount to be made will always produce the optimal result. This is not automatically the case, though: if the coin denominations were 1, 3 and 4, then to make 6, the greedy algorithm would choose three coins (4,1,1) whereas the optimal solution is two coins (3,3).
Related problems
The "optimal denomination problem"[1] is a problem for people who design entirely new currencies: What denominations should be chosen for the coins in order to minimize the average cost of making change -- i.e., the average number of coins needed to make change? The version of this problem assumed that the people making change will use the minimum number of coins (from the denominations available). One variation of this problem assumes that the people making change will use the "greedy algorithm" for making change, even when that requires more than the minimum number of coins. Most current currencies use a 1-2-5 series, but some other set of denominations would require fewer denominations of coins or a smaller average number of coins to make change or both.
See also
References
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In its statement, the singapore property listing - website link, government claimed that the majority citizens buying their first residence won't be hurt by the new measures. Some concessions can even be prolonged to chose teams of consumers, similar to married couples with a minimum of one Singaporean partner who are purchasing their second property so long as they intend to promote their first residential property. Lower the LTV limit on housing loans granted by monetary establishments regulated by MAS from 70% to 60% for property purchasers who are individuals with a number of outstanding housing loans on the time of the brand new housing purchase. Singapore Property Measures - 30 August 2010 The most popular seek for the number of bedrooms in Singapore is 4, followed by 2 and three. Lush Acres EC @ Sengkang
Discover out more about real estate funding in the area, together with info on international funding incentives and property possession. Many Singaporeans have been investing in property across the causeway in recent years, attracted by comparatively low prices. However, those who need to exit their investments quickly are likely to face significant challenges when trying to sell their property – and could finally be stuck with a property they can't sell. Career improvement programmes, in-house valuation, auctions and administrative help, venture advertising and marketing, skilled talks and traisning are continuously planned for the sales associates to help them obtain better outcomes for his or her shoppers while at Knight Frank Singapore. No change Present Rules
Extending the tax exemption would help. The exemption, which may be as a lot as $2 million per family, covers individuals who negotiate a principal reduction on their existing mortgage, sell their house short (i.e., for lower than the excellent loans), or take part in a foreclosure course of. An extension of theexemption would seem like a common-sense means to assist stabilize the housing market, but the political turmoil around the fiscal-cliff negotiations means widespread sense could not win out. Home Minority Chief Nancy Pelosi (D-Calif.) believes that the mortgage relief provision will be on the table during the grand-cut price talks, in response to communications director Nadeam Elshami. Buying or promoting of blue mild bulbs is unlawful.
A vendor's stamp duty has been launched on industrial property for the primary time, at rates ranging from 5 per cent to 15 per cent. The Authorities might be trying to reassure the market that they aren't in opposition to foreigners and PRs investing in Singapore's property market. They imposed these measures because of extenuating components available in the market." The sale of new dual-key EC models will even be restricted to multi-generational households only. The models have two separate entrances, permitting grandparents, for example, to dwell separately. The vendor's stamp obligation takes effect right this moment and applies to industrial property and plots which might be offered inside three years of the date of buy. JLL named Best Performing Property Brand for second year running
The data offered is for normal info purposes only and isn't supposed to be personalised investment or monetary advice. Motley Fool Singapore contributor Stanley Lim would not personal shares in any corporations talked about. Singapore private home costs increased by 1.eight% within the fourth quarter of 2012, up from 0.6% within the earlier quarter. Resale prices of government-built HDB residences which are usually bought by Singaporeans, elevated by 2.5%, quarter on quarter, the quickest acquire in five quarters. And industrial property, prices are actually double the levels of three years ago. No withholding tax in the event you sell your property. All your local information regarding vital HDB policies, condominium launches, land growth, commercial property and more
There are various methods to go about discovering the precise property. Some local newspapers (together with the Straits Instances ) have categorised property sections and many local property brokers have websites. Now there are some specifics to consider when buying a 'new launch' rental. Intended use of the unit Every sale begins with 10 p.c low cost for finish of season sale; changes to 20 % discount storewide; follows by additional reduction of fiftyand ends with last discount of 70 % or extra. Typically there is even a warehouse sale or transferring out sale with huge mark-down of costs for stock clearance. Deborah Regulation from Expat Realtor shares her property market update, plus prime rental residences and houses at the moment available to lease Esparina EC @ Sengkang
- ↑
One of the biggest reasons investing in a Singapore new launch is an effective things is as a result of it is doable to be lent massive quantities of money at very low interest rates that you should utilize to purchase it. Then, if property values continue to go up, then you'll get a really high return on funding (ROI). Simply make sure you purchase one of the higher properties, reminiscent of the ones at Fernvale the Riverbank or any Singapore landed property Get Earnings by means of Renting
In its statement, the singapore property listing - website link, government claimed that the majority citizens buying their first residence won't be hurt by the new measures. Some concessions can even be prolonged to chose teams of consumers, similar to married couples with a minimum of one Singaporean partner who are purchasing their second property so long as they intend to promote their first residential property. Lower the LTV limit on housing loans granted by monetary establishments regulated by MAS from 70% to 60% for property purchasers who are individuals with a number of outstanding housing loans on the time of the brand new housing purchase. Singapore Property Measures - 30 August 2010 The most popular seek for the number of bedrooms in Singapore is 4, followed by 2 and three. Lush Acres EC @ Sengkang
Discover out more about real estate funding in the area, together with info on international funding incentives and property possession. Many Singaporeans have been investing in property across the causeway in recent years, attracted by comparatively low prices. However, those who need to exit their investments quickly are likely to face significant challenges when trying to sell their property – and could finally be stuck with a property they can't sell. Career improvement programmes, in-house valuation, auctions and administrative help, venture advertising and marketing, skilled talks and traisning are continuously planned for the sales associates to help them obtain better outcomes for his or her shoppers while at Knight Frank Singapore. No change Present Rules
Extending the tax exemption would help. The exemption, which may be as a lot as $2 million per family, covers individuals who negotiate a principal reduction on their existing mortgage, sell their house short (i.e., for lower than the excellent loans), or take part in a foreclosure course of. An extension of theexemption would seem like a common-sense means to assist stabilize the housing market, but the political turmoil around the fiscal-cliff negotiations means widespread sense could not win out. Home Minority Chief Nancy Pelosi (D-Calif.) believes that the mortgage relief provision will be on the table during the grand-cut price talks, in response to communications director Nadeam Elshami. Buying or promoting of blue mild bulbs is unlawful.
A vendor's stamp duty has been launched on industrial property for the primary time, at rates ranging from 5 per cent to 15 per cent. The Authorities might be trying to reassure the market that they aren't in opposition to foreigners and PRs investing in Singapore's property market. They imposed these measures because of extenuating components available in the market." The sale of new dual-key EC models will even be restricted to multi-generational households only. The models have two separate entrances, permitting grandparents, for example, to dwell separately. The vendor's stamp obligation takes effect right this moment and applies to industrial property and plots which might be offered inside three years of the date of buy. JLL named Best Performing Property Brand for second year running
The data offered is for normal info purposes only and isn't supposed to be personalised investment or monetary advice. Motley Fool Singapore contributor Stanley Lim would not personal shares in any corporations talked about. Singapore private home costs increased by 1.eight% within the fourth quarter of 2012, up from 0.6% within the earlier quarter. Resale prices of government-built HDB residences which are usually bought by Singaporeans, elevated by 2.5%, quarter on quarter, the quickest acquire in five quarters. And industrial property, prices are actually double the levels of three years ago. No withholding tax in the event you sell your property. All your local information regarding vital HDB policies, condominium launches, land growth, commercial property and more
There are various methods to go about discovering the precise property. Some local newspapers (together with the Straits Instances ) have categorised property sections and many local property brokers have websites. Now there are some specifics to consider when buying a 'new launch' rental. Intended use of the unit Every sale begins with 10 p.c low cost for finish of season sale; changes to 20 % discount storewide; follows by additional reduction of fiftyand ends with last discount of 70 % or extra. Typically there is even a warehouse sale or transferring out sale with huge mark-down of costs for stock clearance. Deborah Regulation from Expat Realtor shares her property market update, plus prime rental residences and houses at the moment available to lease Esparina EC @ Sengkang