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// Copyright 2008, 2009 Brady J. Garvin
// This file is part of Covering Arrays by Simulated Annealing (CASA).
// CASA is free software: you can redistribute it and/or modify it
// under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
// CASA is distributed in the hope that it will be useful, but
// WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU General Public License for more details.
// You should have received a copy of the GNU General Public License
// along with CASA. If not, see <http://www.gnu.org/licenses/>.
#include "PascalTriangle.H"
PascalTriangle::PascalTriangle() {
Array<unsigned>root(1);
root[0] = 1;
table.push_back(root);
}
void PascalTriangle::addRows(unsigned targetDepth) {
while (table.size() <= targetDepth) {
unsigned depth = table.size();
Array<unsigned>line(depth + 1);
Array<unsigned>source = table[depth - 1];
table.push_back(line);
line[0] = 1;
for (unsigned column = 1, trail = source[0]; column < depth; ++column) {
line[column] = trail;
line[column] += trail = source[column];
}
line[depth] = 1;
}
}
unsigned PascalTriangle::nCr(unsigned n, unsigned r) {
if (n >= table.size()) {
addRows(n);
}
if (r > n) {
return 0;
}
return table[n][r];
}
PascalTriangle triangle;
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