leetcode 205. Isomorphic Strings
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题目
Given two strings s and t, determine if they are isomorphic.
Two strings are isomorphic if the characters in s can be replaced to get t.
All occurrences of a character must be replaced with another character while preserving the order of characters. No two characters may map to the same character but a character may map to itself.
For example,
Given “egg”, “add”, return true.
Given “foo”, “bar”, return false.
Given “paper”, “title”, return true.
理解
判断两个字符串是否是同分异构,也就是判断两个字符串里面的字符是不是一一对应。
解决
两个map
正向保证不会一个key对应两个value,反向保证不会两个key对应同一个value
public class Solution { public boolean isIsomorphic(String s, String t) { if(s==null && t==null){ return true; }else if(s==null || t==null){ return false; } if(s.length() != t.length()){ return false; } int N = s.length(); Map<Character,Character> map = new HashMap<Character,Character>(); Map<Character,Character> reservedMap = new HashMap<Character,Character>(); for(int i=0; i<N; i++){ if(map.containsKey(s.charAt(i))){ if(map.get(s.charAt(i))!=t.charAt(i)){ return false; } }else{ map.put(s.charAt(i),t.charAt(i)); } if(reservedMap.containsKey(t.charAt(i))){ if(reservedMap.get(t.charAt(i))!=s.charAt(i)){ return false; } }else{ reservedMap.put(t.charAt(i),s.charAt(i)); } } return true; }}
一个map,一个set
map保证不会一个key对应两个value,set保证不会两个key对应同一个value
public class Solution { public boolean isIsomorphic(String s, String t) { if(s==null && t==null){ return true; }else if(s==null || t==null){ return false; } if(s.length() != t.length()){ return false; } int N = s.length(); Map<Character,Character> map = new HashMap<Character,Character>(); Set<Character> set = new HashSet<Character>(); for(int i=0; i<N; i++){ if(map.containsKey(s.charAt(i))){ if(map.get(s.charAt(i))!=t.charAt(i)){ return false; } }else if(set.contains(t.charAt(i))){ return false; }else{ map.put(s.charAt(i),t.charAt(i)); set.add(t.charAt(i)); } } return true; }}
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