题目还是很好的,提供了一种新的思路方向。
细节方面,开始我的判断条件用的dict,不太好,后来debug好了。
另外,注意其中用数组初始化Set的方法:Set<String> dict = new HashSet(Arrays.asList(bank));
还有 Set<String> a = new Hash<>(); 当中前面<>里面加String的原因是提取出来的直接就是String,后面<>指的是接受各种类型。不加<>表示不区分类型,应该和<>是等价的效果。
https://leetcode.com/problems/minimum-genetic-mutation/ // 这个方法特别好 // https://discuss.leetcode.com/topic/63959/c-two-end-bfs-solution-exactly-same-as-127-word-ladder // 提到与 https://leetcode.com/problems/word-ladder/ 127. Word Ladder 题目其实是一模一样的 // 看了一下,的确是的 public class Solution { // 这个题目里面用到了两面BFS的方法,然后通过对字符串的替换,来降低优先级 // 之前另一个题目 Word Ladder里面,用的是一端到另一端的 // 现在这个更巧妙一些,因为从set里面找结果,比遍历set的内容要更高效一些 public int minMutation(String start, String end, String[] bank) { Set<String> dict = new HashSet(Arrays.asList(bank)); if (!dict.contains(end)) { return -1; } Set<String> lessSet = new HashSet(); Set<String> moreSet = new HashSet(); char[] chList = {‘A‘, ‘C‘, ‘G‘, ‘T‘}; lessSet.add(start); moreSet.add(end); int step = 0; while (true) { // wrong: if dict is empty, no need to check more // right: check lessSet if (lessSet.isEmpty()) { return -1; } if (moreSet.size() < lessSet.size()) { Set<String> tmp = lessSet; lessSet = moreSet; moreSet = tmp; } //printSet(lessSet, moreSet, dict); step++; Iterator<String> iter = lessSet.iterator(); Set<String> newSet = new HashSet(); while(iter.hasNext()) { String str = iter.next(); for (int i=0; i<str.length(); i++) { StringBuilder sb =new StringBuilder(str); for (int j=0; j<4; j++) { if (str.charAt(i) == chList[j]) { continue; } sb.setCharAt(i, chList[j]); if (moreSet.contains(sb.toString())) { return step; } if (dict.contains(sb.toString())) { dict.remove(sb.toString()); newSet.add(sb.toString()); } } } } lessSet = newSet; } } private void printSet(Set<String> lessSet, Set<String> moreSet, Set<String>dict) { System.out.printf("Here is lessSet:"); Iterator<String> iter = lessSet.iterator(); while (iter.hasNext()) { System.out.printf("%s,", iter.next()); } System.out.println(); System.out.printf("Here is moreSet:"); iter = moreSet.iterator(); while (iter.hasNext()) { System.out.printf("%s,", iter.next()); } System.out.println(); System.out.printf("Here is dict:"); iter = dict.iterator(); while (iter.hasNext()) { System.out.printf("%s,", iter.next()); } System.out.println(); System.out.println("################"); } }
时间: 2024-11-07 17:30:23