Merge pull request #11 from kvedala/kvedala

make the code neat and clean without global variables

backtracking/graph_coloring.cpp

@@ -1,18 +1,36 @@
+/**
+ * @file
+ * @brief brief one line description here
+ */
 #include <iostream>
 
-/*
- * Number of vertices in the graph
+// created a namespace to ensure all globals and functions are
+// restricted to this file
+namespace {
+/** A utility function to print solution
+ * @param color description
+ * @param V number of vertices in the graph
  */
-#define V 4
+void printSolution(const int *color, int V) {
+    std::cout << "Following are the assigned colors\n";
+    for (int i = 0; i < V; i++) {
+        std::cout << color[i];
+    }
+    std::cout << "\n";
+}
 
-/**
- * Prototypes
+/** A utility function to check if the current color assignment is safe for
+ * vertex v
+ * @tparam V number of vertices in the graph
+ * @param v description
+ * @param graph description
+ * @param color description
+ * @param c description
+ * @returns `true` if ....
+ * @returns `false` if ....
  */
-void printSolution(int color[]);
-
-/* A utility function to check if the current color assignment
-   is safe for vertex v */
-bool isSafe(int v, bool graph[V][V], int color[], int c) {
+template <int V>
+bool isSafe(int v, const bool graph[V][V], const int *color, int c) {
     for (int i = 0; i < V; i++) {
         if (graph[v][i] && c == color[i]) {
             return false;
@@ -21,39 +39,38 @@ bool isSafe(int v, bool graph[V][V], int color[], int c) {
     return true;
 }
 
-/* A recursive utility function to solve m coloring problem */
-void graphColoring(bool graph[V][V], int m, int color[], int v) {
+/** A recursive utility function to solve m coloring problem
+ * @tparam V number of vertices in the graph
+ * @param graph description
+ * @param m description
+ * @param [in,out] color description // used in,out to notify in documentation
+ * that this parameter gets modified by the function
+ * @param v description
+ */
+template <int V>
+void graphColoring(bool graph[V][V], int m, int color[V], int v) {
     // base case:
     // If all vertices are assigned a color then return true
     if (v == V) {
-        printSolution(color);
+        printSolution(color, V);
         return;
     }
 
     // Consider this vertex v and try different colors
     for (int c = 1; c <= m; c++) {
         // Check if assignment of color c to v is fine
-        if (isSafe(v, graph, color, c)) {
+        if (isSafe<V>(v, graph, color, c)) {
             color[v] = c;
 
             // recur to assign colors to rest of the vertices
-            graphColoring(graph, m, color, v + 1);
+            graphColoring<V>(graph, m, color, v + 1);
 
             // If assigning color c doesn't lead to a solution then remove it
             color[v] = 0;
         }
     }
 }
-
-/* A utility function to print solution */
-void printSolution(int color[]) {
-    std::cout << "Following are the assigned colors\n";
-    for (int i = 0; i < V; i++) {
-        std::cout << color[i];
-    }
-
-    std::cout << "\n";
-}
+}  // namespace
 
 /**
  * Main function
@@ -66,6 +83,7 @@ int main() {
     // | /   |
     // (0)---(1)
 
+    const int V = 4;  // number of vertices in the graph
     bool graph[V][V] = {
         {0, 1, 1, 1},
         {1, 0, 1, 0},
@@ -80,6 +98,6 @@ int main() {
         color[i] = 0;
     }
 
-    graphColoring(graph, m, color, 0);
+    graphColoring<V>(graph, m, color, 0);
     return 0;
 }