Add Hamiltonian cycle.

src/algorithms/graph/hamiltonian-cycle/hamiltonianCycle.js

@@ -91,6 +91,7 @@ function hamiltonianCycleRecursive({
         cycle: currentCycle,
       });
 
+      // BACKTRACKING.
       // Remove candidate vertex from cycle path in order to try another one.
       currentCycle.pop();
     }

src/algorithms/uncategorized/n-queens/nQueens.js

@@ -72,6 +72,7 @@ function nQueensRecursive(solutions, previousQueensPositions, queensCount, rowIn
       // Try to place all other queens as well.
       nQueensRecursive(solutions, queensPositions, queensCount, rowIndex + 1);
 
+      // BACKTRACKING.
       // Remove the queen from the row to avoid isSafe() returning false.
       queensPositions[rowIndex] = null;
     }