Generating Hamiltonian Cycles - Backtracking

Author: Matei Andrei

Backtracking/HamiltonianCyclesGenerator.cpp

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+#include <iostream>
+#include <fstream>
+
+using namespace std;
+ifstream fin("hamCycle.in");
+ofstream fout("hamCycle.out");
+
+#define MAX_VERTICES 1001
+
+int matrix[MAX_VERTICES][MAX_VERTICES], numVer;
+int path[MAX_VERTICES], usedVertices[MAX_VERTICES];
+
+bool hasHamCycles = false;
+
+void showHamCycle()
+{
+    hasHamCycles = true;
+    fout<<'{';
+    for(int i = 1; i <= numVer; i++)
+        fout<<path[i]<<' ';
+    fout<<path[1]<<"}\n";
+}
+
+void hamCycle(int k)
+{
+    for(int i = 1; i <= numVer; i++)
+        if(!usedVertices[i])
+            if(matrix[i][path[k-1]] || k == 1)
+            {
+                path[k] = i;
+                usedVertices[i]++;
+                if(k == numVer)
+                {
+                    if(matrix[path[1]][path[numVer]])
+                        showHamCycle();
+                }
+                else
+                    hamCycle(k+1);
+                usedVertices[i]--;
+            }
+}
+
+int main()
+{
+    fin>>numVer;
+    int x, y;
+    while(fin>>x>>y)
+        matrix[x][y] = matrix[y][x] = 1;
+    hamCycle(1);
+    if(!hasHamCycles)
+        fout<<"No hamiltonian cyce could be generated\n";
+    return 0;
+}