implemented graph coloring algorithm in cpp

graphColoringAlgo/greedyGraphColoring/greedyGraphColoring.cpp

@@ -0,0 +1,181 @@
+#include <bits/stdc++.h>
+using namespace std;
+typedef long long ll;
+typedef vector<int> vi;
+typedef pair<int, int> pi;
+typedef vector<vi> vii;
+typedef deque<int> dqi;
+typedef queue<int> qi;
+typedef priority_queue<int> pqi;
+
+#define ll long long int
+#define ld long double
+#define mp make_pair
+#define pb push_back
+#define ppb pop_back
+#define pf push_front
+#define ppf pop_front
+#define all(x) (x).begin(), (x).end()
+#define uniq(v) (v).erase(unique(all(v)), (v).end())
+#define sz(x) (ll)((x).size())
+#define fr first
+#define sc second
+#define rep(i, a, b) for (int i = a; i < b; i++)
+#define mem1(a) memset(a, -1, sizeof(a))
+#define mem0(a) memset(a, 0, sizeof(a))
+#define in(x) cin >> x
+#define tc    \
+    int t;    \
+    cin >> t; \
+    while (t--)
+#define no "NO" << endl
+#define yes "YES" << endl
+#define sp " "
+#define speed                   \
+    cin.sync_with_stdio(false); \
+    cin.tie(NULL);              \
+    cout.tie(NULL);
+
+int npower(int x, int n)
+{
+    int res = 1;
+    while (n)
+    {
+        if (n % 2)
+            res = (res * x);
+        n /= 2;
+        x = (x * x);
+    }
+    return res;
+}
+int modpow(int x, int n, int M)
+{
+    x = x % M;
+    int res = 1;
+    while (n)
+    {
+        if (n % 2)
+        {
+            res = (res * x) % M;
+        }
+        n /= 2;
+        x = (x * x) % M;
+    }
+    return res;
+}
+int gcd(int a, int b)
+{
+    if (!b)
+        return a;
+    return gcd(b, a % b);
+}
+class Graph
+{
+    int V;          // No. of vertices
+    list<int> *adj; // A dynamic array of adjacency lists
+public:
+    // Constructor and destructor
+    Graph(int V)
+    {
+        this->V = V;
+        adj = new list<int>[V];
+    }
+    ~Graph() { delete[] adj; }
+
+    // function to add an edge to graph
+    void addEdge(int v, int w);
+
+    // Prints greedy coloring of the vertices
+    void greedyColoring();
+};
+
+void Graph::addEdge(int v, int w)
+{
+    adj[v].push_back(w);
+    adj[w].push_back(v); // Note: the graph is undirected
+}
+
+// Assigns colors (starting from 0) to all vertices and prints
+// the assignment of colors
+void Graph::greedyColoring()
+{
+    int result[V];
+
+    // Assign the first color to first vertex
+    result[0] = 0;
+
+    // Initialize remaining V-1 vertices as unassigned
+    for (int u = 1; u < V; u++)
+        result[u] = -1; // no color is assigned to u
+
+    // A temporary array to store the available colors. True
+    // value of available[cr] would mean that the color cr is
+    // assigned to one of its adjacent vertices
+    bool available[V];
+    for (int cr = 0; cr < V; cr++)
+        available[cr] = false;
+
+    // Assign colors to remaining V-1 vertices
+    for (int u = 1; u < V; u++)
+    {
+        // Process all adjacent vertices and flag their colors
+        // as unavailable
+        list<int>::iterator i;
+        for (i = adj[u].begin(); i != adj[u].end(); ++i)
+            if (result[*i] != -1)
+                available[result[*i]] = true;
+
+        // Find the first available color
+        int cr;
+        for (cr = 0; cr < V; cr++)
+            if (available[cr] == false)
+                break;
+
+        result[u] = cr; // Assign the found color
+
+        // Reset the values back to false for the next iteration
+        for (i = adj[u].begin(); i != adj[u].end(); ++i)
+            if (result[*i] != -1)
+                available[result[*i]] = false;
+    }
+
+    // print the result
+    for (int u = 0; u < V; u++)
+        cout << "Vertex " << u << " --->  Color "
+             << result[u] << endl;
+}
+
+// Driver program to test above function
+
+void solve()
+{
+
+    Graph g1(5);
+    g1.addEdge(0, 1);
+    g1.addEdge(0, 2);
+    g1.addEdge(1, 2);
+    g1.addEdge(1, 3);
+    g1.addEdge(2, 3);
+    g1.addEdge(3, 4);
+    cout << "Coloring of graph 1 \n";
+    g1.greedyColoring();
+
+    Graph g2(5);
+    g2.addEdge(0, 1);
+    g2.addEdge(0, 2);
+    g2.addEdge(1, 2);
+    g2.addEdge(1, 4);
+    g2.addEdge(2, 4);
+    g2.addEdge(4, 3);
+    cout << "\nColoring of graph 2 \n";
+    g2.greedyColoring();
+}
+int main()
+{
+    speed;
+    // tc
+    {
+        solve();
+    }
+    return 0;
+}