diff --git a/mlrose/fitness.py b/mlrose/fitness.py
index 94a8ffc2..250d43c1 100644
--- a/mlrose/fitness.py
+++ b/mlrose/fitness.py
@@ -904,9 +904,14 @@ class MaxKColor:
     def __init__(self, edges):
 
         # Remove any duplicates from list
-        edges = list({tuple(sorted(edge)) for edge in edges})
-
-        self.edges = edges
+        self.neighbors = {}
+        for v1, v2 in edges:
+            if v1 not in self.neighbors:
+                self.neighbors[v1] = set()
+            if v2 not in self.neighbors:
+                self.neighbors[v2] = set()
+            self.neighbors[v1].add(v2)
+            self.neighbors[v2].add(v1)
         self.prob_type = 'discrete'
 
     def evaluate(self, state):
@@ -925,9 +930,9 @@ def evaluate(self, state):
 
         fitness = 0
 
-        for i in range(len(self.edges)):
-            # Check for adjacent nodes of the same color
-            if state[self.edges[i][0]] == state[self.edges[i][1]]:
+        for v, color in enumerate(state):
+            # Check that all adjacent nodes are different color
+            if all(state[neighbor] != color for neighbor in self.neighbors.get(v, set())):
                 fitness += 1
 
         return fitness