RosettaCodeData/Task/Graph-colouring/C++/graph-colouring.cpp

114 lines
3.4 KiB
C++

#include <algorithm>
#include <cstdint>
#include <iostream>
#include <map>
#include <set>
#include <sstream>
#include <string>
#include <unordered_set>
#include <vector>
const std::vector<std::string> all_colours = { "PINK", "ORANGE", "CYAN", "YELLOW", "RED", "GREEN", "BLUE" };
class Node {
public:
Node(const int32_t& aID, const int32_t& aSaturation, const std::string& aColour)
: id(aID), saturation(aSaturation), colour(aColour) {}
Node() : id(0), saturation(0), colour("NO_COLOUR") {}
int32_t id, saturation;
std::string colour;
bool excluded_from_search = false;
};
int main() {
std::map<int32_t, Node, decltype([](const int32_t& a, const int32_t& b){ return a < b; })> graph;
std::map<int32_t, std::set<int32_t, decltype([](const int32_t& a, const int32_t& b) { return a < b; })>,
decltype([](const int32_t& a, const int32_t& b) { return a < b; })> neighbours;
const std::vector<std::string> graph_representations = { "0-1 1-2 2-0 3",
"1-6 1-7 1-8 2-5 2-7 2-8 3-5 3-6 3-8 4-5 4-6 4-7",
"1-4 1-6 1-8 3-2 3-6 3-8 5-2 5-4 5-8 7-2 7-4 7-6",
"1-6 7-1 8-1 5-2 2-7 2-8 3-5 6-3 3-8 4-5 4-6 4-7" };
for ( const std::string& graph_representation : graph_representations ) {
graph.clear();
neighbours.clear();
std::stringstream stream(graph_representation);
std::string element;
while ( stream >> element ) {
if ( element.find("-") != std::string::npos ) {
const int32_t id1 = element[0] - '0';
const int32_t id2 = element[element.length() - 1] - '0';
if ( ! graph.contains(id1) ) {
graph[id1] = Node(id1, 0, "NO_COLOUR");
}
Node node1 = graph[id1];
if ( ! graph.contains(id2) ) {
graph[id2] = Node(id2, 0, "NO_COLOUR");
}
Node node2 = graph[id2];
neighbours[id1].emplace(id2);
neighbours[id2].emplace(id1);
} else {
const int32_t id = element[0] - '0';
if ( ! graph.contains(id) ) {
graph[id] = Node(id, 0, "NO_COLOUR");
}
}
}
for ( uint64_t i = 0; i < graph.size(); ++i ) {
int32_t max_node_id = -1;
int32_t max_saturation = -1;
for ( const auto& [key, value] : graph ) {
if ( ! value.excluded_from_search && value.saturation > max_saturation ) {
max_saturation = value.saturation;
max_node_id = key;
}
}
std::unordered_set<std::string> colours_used;
for ( const int32_t& neighbour : neighbours[max_node_id] ) {
colours_used.emplace(graph[neighbour].colour);
}
std::string min_colour;
for ( const std::string& colour : all_colours ) {
if ( ! colours_used.contains(colour) ) {
min_colour = colour;
}
}
graph[max_node_id].excluded_from_search = true;
graph[max_node_id].colour = min_colour;
for ( int32_t neighbour : neighbours[max_node_id] ) {
if ( graph[neighbour].colour == "NO_COLOUR" ) {
graph[neighbour].saturation = colours_used.size();
}
}
}
std::unordered_set<std::string> graph_colours;
for ( const auto& [key, value] : graph ) {
graph_colours.emplace(value.colour);
std::cout << "Node " << key << ": colour = " + value.colour;
if ( ! neighbours[key].empty() ) {
std::cout << std::string(8 - value.colour.length(), ' ') << "neighbours = ";
for ( const int32_t& neighbour : neighbours[key] ) {
std::cout << neighbour << " ";
}
}
std::cout << std::endl;
}
std::cout << "Number of colours used: " << graph_colours.size() << std::endl << std::endl;
}
}