GraphColoringCSP.cpp

#include <algorithm>
#include <cctype>
#include <climits>
#include <cmath>
#include <iostream>
#include <map>
#include <memory>
#include <queue>
#include <set>
#include <sstream>
#include <string>
#include <unordered_map>
#include <unordered_set>
#include <utility>
#include <vector>
using namespace std;

int V = 4;
int M = 3;
vector<int> color(4, 0);
vector<vector<bool>> graph = {
    {false, true, true, false},
    {true, false, true, true},
    {true, true, false, true},
    {false, true, true, false}
};

bool canColor(int vertex, int c) {
    for (int i = 0; i < V; ++i) {
        if (graph[vertex][i] && color[i] == c) return false;
    }
    return true;
}

bool solve(int vertex) {
    if (vertex == V) return true;
    for (int c = 1; c <= M; ++c) {
        if (canColor(vertex, c)) {
            color[vertex] = c;
            if (solve(vertex + 1)) return true;
        }
    }
    return false;
}

int main() {
    if (solve(0)) {
        cout << "Graph coloring found:\n";
        for (int i = 0; i < V; ++i) {
            cout << "Vertex " << i << " -> Color " << color[i] << '\n';
        }
    } else {
        cout << "No valid coloring found with " << M << " colors.\n";
    }
    return 0;
}