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/* Tyler R. Richard |
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10/21/10 |
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This program uses sets to determine all the candidate keys and |
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all non trivial closures of a given a list of |
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single letter attributes and a set of functional dependences. |
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TODO: |
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-make it find canonical covers |
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*/ |
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#include <iostream> |
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#include <cmath> |
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#include <algorithm> |
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#include <vector> |
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#include <string> |
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#include <map> |
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#include <set> |
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|
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using namespace std; |
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|
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set<char> setize(string data) { |
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set<char> retval; |
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for(int i = 0; i < data.size(); i++) { |
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retval.insert(data[i]); |
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} |
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return retval; |
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} |
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|
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int comp(set<char> a, set<char> b) { |
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if(a.size() == b.size()) { |
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return(a < b); |
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}else{ |
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return(a.size() < b.size()); |
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} |
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} |
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|
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string printSet(set<char> data) { |
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string retval; |
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for(set<char>::iterator p = data.begin(); p != data.end(); p++) { |
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retval += *p; |
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} |
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return(retval); |
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} |
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|
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int main() { |
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set<char> full_set; |
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string determinant, product; |
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map<set<char>,set<char> > F; |
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map<set<char>,set<char> >::iterator it; |
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cin >> determinant; |
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full_set = setize(determinant); |
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int n; |
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cin >> n; |
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// read in the functionality det pairs in |
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for(int i =0; i < n; i++) { |
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cin >> determinant >> product >> product; |
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set<char> dets = setize(determinant); |
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set<char> prods = setize(product); |
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F[dets].insert(prods.begin(), prods.end()); |
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} |
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// create a list of possible inputs |
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unsigned int bitmask = 0; |
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vector<char> v; |
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vector<set<char> > possible_keys; |
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|
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for(set<char>::iterator i = full_set.begin(); i != full_set.end(); i++) { |
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v.push_back(*i); |
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} |
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// assume # of attributes < 32 |
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while(bitmask <= 1<<v.size()){ |
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bitmask++; |
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unsigned int index = 1; |
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set<char> dets; |
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for(int i = 0; i < v.size(); i++ ) { |
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if(index & bitmask) { |
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dets.insert(v[i]); |
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} |
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index = index << 1; |
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} |
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possible_keys.push_back(dets); |
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} |
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sort(possible_keys.begin(), possible_keys.end(),comp); |
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vector<set<char> > found_keys; |
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for(int i = 0; i < possible_keys.size(); i++) { |
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//cout << printSet(possible_keys[i]); |
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set<char> dets = possible_keys[i]; |
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bool cont = true; |
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for(int j =0 ; j < found_keys.size(); j++) { |
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if(includes( |
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dets.begin(), dets.end(), |
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found_keys[j].begin(), found_keys[j].end()) |
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){ |
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//this key is a super set of a key we've already discovered |
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cont = false; |
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break; |
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} |
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} |
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if(!cont){ |
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continue; |
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} |
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bool changes = true; |
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while(changes && dets.size() != full_set.size()) { |
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changes = false; |
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for(it = F.begin();it != F.end() && dets.size() != full_set.size() |
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; it++) { |
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if(includes(dets.begin(), dets.end(), |
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it->first.begin(),it->first.end()) && |
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!includes(dets.begin(), dets.end(), |
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it->second.begin(), it->second.end())){ |
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// cout << it->first.size() << " " << dets.size() << endl; |
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dets.insert(it->second.begin(),it->second.end()); |
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changes = true; |
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} |
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} |
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} |
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/* Print the keys that the given det can get to |
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for(set<char>::iterator p=dets.begin(); p != dets.end(); p++) { |
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cout << *p; |
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} |
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*/ |
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|
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cout << printSet(possible_keys[i]); |
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cout << " = "; |
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cout << printSet(dets); |
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if(dets.size() == full_set.size()) { |
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found_keys.push_back(possible_keys[i]); |
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cout << " is a candidate key!"; |
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} |
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cout << endl; |
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} |
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} |