Find Chess960 starting position identifier: Difference between revisions
Find Chess960 starting position identifier (view source)
Revision as of 20:07, 21 July 2023
, 9 months agoMoved post to correct position.
m (Posted in wrong position. Error being caused by multiple BASIC posts.) Tag: Manual revert |
m (Moved post to correct position.) |
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SP-ID = 617
</pre>
=={{header|C++}}==
<syntaxhighlight lang="c++">
#include <algorithm>
#include <cstdint>
#include <stdexcept>
#include <iostream>
#include <string>
#include <map>
#include <set>
#include <vector>
const std::set<std::pair<char, int32_t>> correct_pieces = { std::make_pair('R', 2), std::make_pair('N', 2),
std::make_pair('B', 2), std::make_pair('Q', 1), std::make_pair('K', 1) };
std::map<std::vector<int32_t>, int32_t> knights_table = {
{ std::vector<int32_t>{ 0, 1 }, 0 },
{ std::vector<int32_t>{ 0, 2 }, 1 },
{ std::vector<int32_t>{ 0, 3 }, 2 },
{ std::vector<int32_t>{ 0, 4 }, 3 },
{ std::vector<int32_t>{ 1, 2 }, 4 },
{ std::vector<int32_t>{ 1, 3 }, 5 },
{ std::vector<int32_t>{ 1, 4 }, 6 },
{ std::vector<int32_t>{ 2, 3 }, 7 },
{ std::vector<int32_t>{ 2, 4 }, 8 },
{ std::vector<int32_t>{ 3, 4 }, 9 } };
void validate(const std::string& position) {
if ( position.length() != 8 ) {
throw std::invalid_argument("Chess position has invalid length" + std::to_string(position.length()));
}
std::map<char, int32_t> position_map;
for ( const char& ch : position ) {
if ( position_map.find(ch) == position_map.end() ) {
position_map.emplace(ch, 1);
} else {
position_map[ch]++;
}
}
std::set<std::pair<char, int32_t>> pieces;
std::transform(position_map.begin(), position_map.end(), std::inserter(pieces, pieces.begin()),
[](const std::pair<char, int32_t>& entry) { return entry; });
if ( pieces != correct_pieces ) {
throw std::invalid_argument("Chess position contains incorrect pieces.");
}
const std::vector<uint64_t> bishops = { position.find_first_of('B'), position.find_last_of('B') };
if ( ( bishops[1] - bishops[0] ) % 2 == 0 ) {
throw std::invalid_argument("Bishops must be on different coloured squares.");
}
std::vector<uint64_t> rook_king =
{ position.find_first_of('R'), position.find_first_of('K'), position.find_last_of('R') };
if ( ! ( rook_king[0] < rook_king[1] && rook_king[1] < rook_king[2] ) ) {
throw std::invalid_argument("The king must be between the two rooks.");
}
}
int32_t calculate_SPID(std::string& position) {
const int32_t index_one = position.find_first_of('B');
const int32_t index_two = position.find_last_of('B');
const int32_t D = ( index_one % 2 == 0 ) ? index_one / 2 : index_two / 2;
const int32_t L = ( index_one % 2 == 0 ) ? index_two / 2 : index_one / 2;
position.erase(remove_if(position.begin(), position.end(),
[](const char& ch){ return ch == 'B'; }), position.end());
const uint64_t Q = position.find_first_of('Q');
position.erase(remove_if(position.begin(), position.end(),
[](const char& ch){ return ch == 'Q'; }), position.end());
const int32_t N =
knights_table[ { (int32_t) position.find_first_of('N'), (int32_t) position.find_last_of('N') } ];
return 96 * N + 16 * Q + 4 * D + L;
}
int main() {
std::vector<std::string> positions = { "QNRBBNKR", "RNBQKBNR", "RQNBBKRN", "RNQBBKRN" };
for ( std::string& position : positions ) {
validate(position);
std::cout << "Position " << position << " has Chess960 SP-ID = " << calculate_SPID(position) << std::endl;
}
}
</syntaxhighlight>
{{ out }}
<pre>
Position QNRBBNKR has Chess960 SP-ID = 105
Position RNBQKBNR has Chess960 SP-ID = 518
Position RQNBBKRN has Chess960 SP-ID = 601
Position RNQBBKRN has Chess960 SP-ID = 617
</pre>
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