89 lines
1.6 KiB
C++
89 lines
1.6 KiB
C++
|
#include "pascal_triangle.h"
|
||
|
#include <cstdio>
|
||
|
|
||
|
using namespace ogu;
|
||
|
|
||
|
PascalTriangle ptriang;
|
||
|
|
||
|
void PascalRow::setFromPrevious(const PascalRow& prev)
|
||
|
{
|
||
|
k = prev.k + 1;
|
||
|
clear();
|
||
|
prolong(prev);
|
||
|
}
|
||
|
|
||
|
/** This prolongs the PascalRow. If it is empty, we set the first item
|
||
|
* to k+1, which is noverk(k+1,k) which is the second item in the real
|
||
|
* pascal row, which starts from noverk(k,k)=1. Then we calculate
|
||
|
* other items from the provided row which must be the one with k-1.*/
|
||
|
void PascalRow::prolong(const PascalRow& prev)
|
||
|
{
|
||
|
if (size() == 0)
|
||
|
push_back(k+1);
|
||
|
int last = back();
|
||
|
for (unsigned int i = size(); i < prev.size(); i++) {
|
||
|
last += prev[i];
|
||
|
push_back(last);
|
||
|
}
|
||
|
}
|
||
|
|
||
|
void PascalRow::prolongFirst(int n)
|
||
|
{
|
||
|
// todo: check n = 1;
|
||
|
for (int i = (int)size()+2; i <= n; i++)
|
||
|
push_back(i);
|
||
|
}
|
||
|
|
||
|
void PascalRow::print() const
|
||
|
{
|
||
|
printf("k=%d\n",k);
|
||
|
for (unsigned int i = 0; i < size(); i++)
|
||
|
printf("%d ",operator[](i));
|
||
|
printf("\n");
|
||
|
}
|
||
|
|
||
|
int PascalTriangle::max_n() const
|
||
|
{
|
||
|
return (int)(tr[0].size()+1);
|
||
|
}
|
||
|
|
||
|
int PascalTriangle::max_k() const
|
||
|
{
|
||
|
return (int)tr.size();
|
||
|
}
|
||
|
|
||
|
void PascalTriangle::ensure(int n, int k)
|
||
|
{
|
||
|
// add along n
|
||
|
if (n > max_n()) {
|
||
|
tr[0].prolongFirst(n);
|
||
|
for (int i = 2; i <= max_k(); i++)
|
||
|
tr[i-1].prolong(tr[i-2]);
|
||
|
}
|
||
|
|
||
|
if (k > max_k()) {
|
||
|
for (int i = max_k()+1; i <= k; i++) {
|
||
|
PascalRow r;
|
||
|
tr.push_back(r);
|
||
|
tr.back().setFromPrevious(tr[i-2]);
|
||
|
}
|
||
|
}
|
||
|
}
|
||
|
|
||
|
int PascalTriangle::noverk(int n, int k)
|
||
|
{
|
||
|
// todo: rais if out of bounds
|
||
|
if (n-k < k)
|
||
|
k = n-k;
|
||
|
if (k == 0)
|
||
|
return 1;
|
||
|
ensure(n, k);
|
||
|
return (tr[k-1])[n-1-k];
|
||
|
}
|
||
|
|
||
|
void PascalTriangle::print() const
|
||
|
{
|
||
|
for (unsigned int i = 0; i < tr.size(); i++)
|
||
|
tr[i].print();
|
||
|
}
|