Leetcode 433 Minimum Genetic Mutation

Author: jiajionline

0433_Minimum Genetic Mutation/MinimumGeneticMutation_DFS.java

@@ -6,10 +6,10 @@ public int minMutation(String start, String end, String[] bank) {
  char[] GENES = new char[]{'A','C','G','T'};
  Set<String> banks = new HashSet<String>();
  for(String b : bank) banks.add(b);
+ if(!banks.contains(end)) return -1;
  banks.add(start);
 
- Set<String> visited = new HashSet();
- DFS(banks, visited, start, 0, GENES, end);
+ DFS(banks, new HashSet(), start, 0, GENES, end);
 
  return ans == Integer.MAX_VALUE ? -1 : ans;
  }
@@ -26,13 +26,14 @@ private void DFS(Set<String> banks, Set<String> visited, String g, int mutations
  char[] chars = g.toCharArray();
 
  for(int i=0;i<chars.length;i++) {
+ char oldChar = chars[i];
  for(int j=0; j < GENES.length; j++) {
- char oldChar = chars[i];
+ if(oldChar == GENES[j]) continue;
  chars[i] = GENES[j];
  String newGene = new String(chars);
  DFS(banks, visited, newGene, mutations+1, GENES, end);
- chars[i] = oldChar;
  }
+ chars[i] = oldChar;
  }
  }
 }