205. Isomorphic Strings | 判断两个字符串形式是否相同

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.

Note:
You may assume both s and t have the same length.

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思路:用两个hash数组，分别记录s和t的字符的下一个相同的位置，如果没有下一个相同的，则是当前位置，创造hash数组时从后往前遍历两个字符串的字符。

public class Solution {  public boolean isIsomorphic(String s, String t) {      if (s.length() == 0) {return true;}int hashs[] = new int[256];int hasht[] = new int[256];int len = s.length();int hashnexts[] = new int[s.length()];int hashnextt[] = new int[t.length()];hashnexts[len - 1] = hashnextt[len - 1] = len - 1;for (int i = len - 1; i >= 0; i--) {if (hashs[s.charAt(i)] > 0) {hashnexts[i] = hashs[s.charAt(i)];}if (hasht[t.charAt(i)] > 0) {hashnextt[i] = hasht[t.charAt(i)];}hashs[s.charAt(i)] = i;hasht[t.charAt(i)] = i;}for (int j = 0; j < len; j++) {if (hashnexts[j] != hashnextt[j]) {return false;}}return true;}}